Are you looking for a strategy game which involves intense tactical action across time? If you are, then you can keep looking, because this isn't it.
Interestingly enough, the main issue with Achron is the time travel mechanics themselves. In theory it sounds about right: Use future knowledge to plan your strategy, or fix past mistakes. It worked well enough for Prince of Persia. Where could it possibly go wrong?
Time waves. That's where it first starts going horribly wrong. In theory, you should be able to jump to the past, make a few fixes, and then jump back to the present and see the results, right? Wrong. You have to wait for the "time wave" to hit, and erase the incorrect present. And how long would that take? Well, as long as you've jumped back. The time waves only move at double speed compared to normal playing. During that time, you have to play in the past, at double speed, or at least re-watch it.
You can't keep playing in the present, because as soon as the time-wave hits, many of your orders will actually be wrong for the situation, if they remain valid at all. And that's assuming that the units to whichyou need to give orders even exist in the present. You can't just wait, either, because the present doesn't stop, and by the time the time wave reaches that "future event" to which you were reacting, it is already, itself, far in the past. So, even if you only make one change, and let everything else play out without interaction, you still have to play in the past just to continue from the same spot that was previously the present. It probably wouldn't be so bad if time waves moved at 5 or 10 times the speed of normal play.
Most of the time, it's best to just play in the present, or even a bit in the future. If you need to "undo past mistakes", save games work much better than time travel. Of course, this all goes flying out the window once you have an achronal enemy. The AI seems to thrive on playing in the past. And every time the enemy makes a change, you have to go back and re-watch the whole thing, because it's enough that one of your units moved 3 inches left for most of your future commands to not work. And there's nothing more annoying than taking out the last of your enemy units, only for a time-wave to hit and suddenly your whole army is gone and you don't know why. Be prepared to watch the timeline UI VERY closely, because it's not too obvious when major changes occur. And, of course, if you notice it only when it hits the present, then it is far too late to go back and fix things, since, as said before, time waves are VERY slow.
Once you get past the idea of having to replay or at least review the same section of time over and over, you're hit with chrono-energy. In a time when most RTS players pride themselves on their click-rate, you get a game that actually tells you that the number of clicks you have is limited, and horribly so. Forget micro-managed tactics, it'd be too easy for the enemy to screw them all up by changing one tiny thing, and it would cost too much chrono-energy to undo and redo them when that happens.
It probably wouldn't be so bad if you were just limited to not making too many CHANGES to the past. But, as noted above, you are often forced to play completely in the past, unable to jump back to the present, so you're actually being limited on the number of actual practical things you can do throughout play.
But the worst part isn't in how little control you're allowed, but rather how the game tries to compensate for it. It seems like decades of RTS evolution were thrown down the drain, and instead you get a control scheme that is worse than what Dune 2 had. Since group commands cost as much chrono-energy as individual commands, you're supposed to organize units into "hierarchies", where giving orders to "the leader" gives that order to the rest of the group. As tedious as it is to arrange these heirarchies, it becomes even worse to control them. Beside having to keep track of "whose the leader", be sure that a command asking them all to move to one place will send them all scattering in all directions.
And yeah, by the way, if going up against an achronal enemy, you can be sure your leader will be targetted back in time, rendering all of your commands invalid. Sure would have been easier to spot major time waves if the "advanced timeline UI" had an indicator for "given a command to a dead unit".
The units also have individual AIs so that you won't have to give them commands to do every little thing. Too bad the AI is horrible, forcing you to waste tons of chrono-energy trying to tell your units NOT to move. Too bad there's no "stop" command. There's an "idle" command, which basically means "stop doing what I say, and go commit suicide instead". I'm not asking for Supreme Commander level of unit AI and control here, I'd just settle for my units following orders.
And all that is AFTER you've the "undo" command - the command you are going to be using the most, as you repeatedly replay the same section of events.
Once you take away the utterly broken time mechanics, what you're left with is a rather poorly balanced strategy game, with really poor controls. There are a few units which are clearly more powerful than anything else, and they aren't significantly more expensive to create. In fact, some of them are actually cheaper than other units. A group of 5 octoligos or twin MARs can take out most anything. Except for an army of MCBs or black birds. Units with self-repair tend to have the most broken balance, as they are neigh-invincible, so long as you can convince them not to move too far from each other (See: Horrible controls). I guess that's the reason only the humans have them. I spent most of chapter 3 just making sure the one MCB I had was free to join the fight, since it was usually a game-breaker. Oddly enough, I got an achievement for it, even though it was the most obvious thing to do.
If you're thinking of creating mixed armies of aerial and ground units with anti-air and anti-ground, you can forget it. It would require too much micro-management to use these properly, and that, as noted before, gets screwed over fast, thanks to the time mechanics. You'd think the per-unit AI, given that it's probably intended to reduce the need for micro-management, would do something useful, like targetting aerial units with anti-air and ground units with anti-ground, but it seems to more often do the exact opposite. Fact is, it's better to just have a large enough all-purpose army, which can simply be told to go from point A to point B and destroy everything in its path. That tactic works WAY better than it should. Probably because, no matter how many times the enemy replays the battle with the overly large army, there is nothing it can do to prevent the resulting annihilation.
The main counter-measure the game offers to the "large enough army of all the same unit" is limited resources. And most maps sure do limit resources. Of course, there's nothing like using every last resource to build a huge army, destroying all of the enemy's units, and then getting a surprise mission to "build this and that" with resources you no longer have.
So, having covered how bad the game is all on its own, let's get started on the bugs. And this game sure is rife with them.
Let's start with the simplest one: Windowed mode does not work. I mean, it works, but the graphics are scaled based on the total window size, including the title. This makes the top of the screen be cut off. Too bad that's exactly where your resources are shown. The thing is, this should have been the first thing that should have shown up on even the simplest QA. It's like no one even tested if the game manages to go to windowed mode.
There's more I'd like to say, but it seems I'm out of room in this review (Why is this limited?). Suffice to say, there are worse bugs, but not enough space left. You have been warned.