When I first started playing, back in early 2012, my first impression was overwhemingly positive. Although the progression system was quite close to the current one (level based gear with module slots), the game showed enormous promise to become its own "thing".
It started with 0.5, where the new tech tree involved a much more horizontal progression, which was less about inflating numbers and more broadifying your combat options. It also brought in a constraint system (fixed at the time), which forced you to make decisions about the gear you could equip. It sounds like a bad thing on paper, but it actually made you *think* about your character. You could decide exactly how to build it, how to specialize it. Your character was truly one you'd call your own.
Another milestone passed, and the tech tree was refined in a deep, complex crafting system while the character progression focused on constraints (which became upgradeable through gained experience and collected resources). As your constraints improved, you could equip stronger, better gear (bringing some vertical progression) while making sure you could never equip all of the top quality ones at the same time.
It was an ideal diagonal progression system, one that I sincerely hoped would stay for good.
As for the world, well... we were promised an open, sandbox-ish world that would evolve and change through the players' actions, and for a time we had something quite close.
Coral Forest used to be quite a dangerous place where watchtowers and other key points could fall to the Chosen any time if left undefended. Places like Sunken Harbor and Thump Dump could even be submerged by the Melding, and that had consequences, albeit temporary.
Still, we really had the feeling that the region was the last bastion of humanity surrounded by an implacable force from another world.
And most importantly, anyone could contribute to an event (ares missions, thumpers, melding tornados and so on...) and be equally rewarded regardless of his own progression.
So, what happened?
Well, progression is now back to being level-based with slottable gear and no constraints. The consequence is you don't need to care about your character, you just pile up level after, equip that white Gun'O'Pwn because it's better than your old purple Gun'O'Whack you picked up 5 levels ago, you see numbers inflate exponentially and it doesn't mean crap because your enemies' health increased by the same factor, you follow the same jobs over and over since they're all variant of kill/fetch/escort (Yep, there are escort missions. The kind that makes you ragequit 99% of the time).
The crafting system has been simplified to the point of being dumbed down, yet at the same time required several times more material grinding than before, especially when some components can only be gotten through the goodwill of the RNG.
Said RNG also govern the result of your craft, so you are not even sure if the result is what you want.
The old open world has been segregated into level-based areas, so players too high or too low for an ares mission, job or whatever would be penalized in the rewards gained (that's right, if you are a lowbie and want to try something challenging, you are screwed).
Virtually all of the 'chosen war' aspect have been taken out of coral forest. No invasions, no incursions, a few strike teams every once in a while... the "last bastion of humanity" became a dull, unchanging place.
With the release patch, the game changed from an innovative, off-the-beaten-track MMOFPS into essentially WoW with guns. It had a lot of promise, but instead went the generic, unimaginative way.
I regularly played this game for two years and enjoyed the hell out of it. I just don't any more the way it is now.
For people who never played the beta, you might enjoy it. You just wouldn't realize how good it could have been.