Bit Planet has done some very cool things with this game.
Normally, I would hit the good points first, but I want to get my complaints out of the way.
On the plot side, the characterizations of the different pilots can be pretty cartoony, to the point of things becoming unbelievable. Lieutenants have an alarming tendency to order captains (and even generals) around, and it's done with complete impunity. It was hard for me to suspend my disbelief in that area. Further, there is an outsized amount of profanity used by a particular pilot, and it seems to be gratuitous rather than character establishing. (Maybe it's just me.)
Speaking technically, the game does have some nagging, but mercifully un-fatal bugs. The first is that the Ingress/ hacking loop still delivers invalid codes in some situations. It's incredibly frustrating to select what should be the right code, only to have it fail...and be taking fire from a number of turrets at the same time. Also, there's an occasional graphics glitch where a "sun" overlay gets plastered all over the center of your screen. (The problem can be quickly fixed by selecting a different screen resolution, and then reverting.)
Every once in a while, a rough edge in overall experience design makes a glaring appearance. The most notable of these was a mission where you have to save some transports that are dropping through atmosphere. The success/ fail conditions for the mission are not at all clear at first, although the success condition is so low that I suppose you can shrug your shoulders a bit.
My final negative point is that "jinking" in a tough dogfight doesn't seem to be possible. If an enemy fighter succeeds in getting you "zeroed," you either have afterburners available for escape, or you're in big trouble. The only turning option you have seems to be heading directly toward your attacker, which lets them hammer you several more times before they overshoot. Hopefully, you're not in a crowd.
But the above paragraph leads me into what's really, really good about the game:
There are lots of other space sims that give you the ability to transfer energy amongst three systems, such as shields, weapons, and afterburner. In every other such game that I've played, that energy management is fairly secondary. In "Battle Of Sol," it's front and center in a very neat and satisfyingly challenging way. Especially when flying the Hades(?), each energy reserve is pretty shallow. You have to keep your head in the ETS game, or you will be in enormous trouble. This lends a nice boost to the tension of combat, especially because the basic dogfighting isn't all that hard.
The criticality of the energy management also helps to create noticeable differentiation between the Hades and the Arrow fighters. Arrows don't let you manage energy transfer manually, and the afterburners are "all or nothing," but the regen time is fast...for two out of three systems. The bugbear you get to wrestle with is that shield regeneration isn't under your control - you have to escape from combat almost entirely if your Arrow gets mangled. This "personality difference" really keeps you on your toes, and is a great way to add variety where a whole bunch of different ships aren't a gameplay option.
Another great choice by the developers is the need to master the "slide" mechanic. In other games, the ability to keep your heading while changing your orientation is handy, if not necessarily required. In this game, you'll either get it or get torn to shreds. Giving thought to your heading and then engaging a slide is the only thing that will keep you effective against gun platforms and capital ships. Once you do get it, you'll feel very much more like an ace pilot, especially since you'll actually be able to do some good.
Another thing I like was the (seeming) overall homage to the reimagined "Battlestar Galactica." The UCS missions often feature percussion-heavy music that would fit right in with BSG, and the Hades guns seem to behave - and sound - very much like what you would find on a Colonial Viper. Maybe this was all intentional, and maybe it wasn't...but it's fun either way, and made me smile.
Bit Planet has really done some fine work here, and I think they could build a real challenger to Wing Commander and Freespace if they keep iterating and extending what they've got already. This particular game isn't an instant classic, mosty because it's not deep enough for that, but the seeds do seem to be there.