Well, my impressions so far:
Combat:
Soloing is quite decent in space, fairly boring on the ground. Bridge Commander did some things a lot better, to be honest. The real fun, however, is fighting together with others, which makes ground battles fun and space battles really good!
Some weapon types (Phasers vs. Disruptors) seem very similar, making it fairly irrelevant which one you go with as long as you pick the appropriate skills for those weapon types.
Photon vs. Quantum torpedoes are more noticable, as the former reloads faster, but the latter does a bit more damage per hit. Here you get to choose based on whether you think you will have a clear shot often enough to make the Photons worth it over the Quantums or not.
Cannons vs. Beam Array are an interesting choice to make. Cannons do a lot of damage, but have something like a 45 degree firing arc (I think), while Beam Arrays have around 210 degree firing arcs, but with lower damage. Once again, choice will be based on how you want to battle (flying around them or gunning straight down their throats).
Missions:
There are the usual MMO missions, like killing x amount of enemies, fetching/delivering things etc. Many missions send you out to investigate something, has you finding enemies causing trouble, killing said enemies, rescuing hostages or recovering stolen items. Some include setting/disarming explosives on various secret weapons, buildings or whatnot. Not entirely uncommon are missions that include both space and ground objectives in a linear fashion.
There are some missions that were at least interesting the first time around (don't know how I'll feel about them if I bring another character through them), like some time-travel, a very familiar device of destruction from TOS (played that one today in a group, really enjoyed it). There are some pretty decent mission "stories" in there from time to time, but far from all of them are great or anything like that.
There are fleet actions, as well, where a large number of players do the same mission, like repelling a klingon invasion, that can be pretty intense. As a new player, I made the mistake of getting too close to 10 or so larger enemy ships and was killed in a few seconds.
Lore:
Lots of references to events, places, people, some minor characters even show up. Theoretically, you should be able to do a simplified variant of "the Riker manouver" from Insurrection, but I never got a ship in the right position to try.
Leonard Nimoy as the occasional "narrator" is a nice touch, and I think it's good that he only seems to speak once for every new sector block you enter (four times for me, so far), it would probably be too much otherwise.
Stability:
The game seems to be mostly stable now. I had heard of the problems during Beta and Head Start, but it seems to work pretty well after the latest patches. I've only been disconnected when I missed that the server(s) was/were being taken down for maintenance. Occasionally, there is a "Server not responding" message and other delays during area transitions and loading screens when doing missions as a group, but it hasn't been much to complain about yet.
All in all, nothing game-breaking so far, mostly just a visual glitch here or delay there.
Various:
- Haven't seen much of real exploration yet, a bit disappointing.
- The "not-true-3D" argument I'm not sure about. I think many find it easier to play it this way (and the series/movies mostly did it this way, too), but it is a valid point to consider.
- The sector space view is pretty boring with all it's grids, blue lines of some kind, solar-systems-on-a-stick and so on, but it gets the job done most of the time. Still, could probably have been done quite a bit better. It's also pretty small, and you move quite slowly through it. Speeding up the movement and having a larger game area would have been better for the feeling of movement, as well as for fitting more players per instance.
- Crafting seems to be pretty problematic for many, with lacking documentation and similar. Few people know anything about how much work one needs to put into the Tier 1 crafting in order to move upwards, and most of the stuff you can make seem less than necessary even as a Liutenant Commander grade 3.
- Pre-order bonuses were a bit bugged, but seem mostly fixed now. I haven't seen any really game-breaking/-altering bonuses, to be honest, seems to be primarily for fun. I got the Liberated Borg Bridge Officer, which is good and cool, but nowhere near overpowered as far as I've seen. It's mostly starting ships, a decent starter weapon for ground combat, special uniforms or such. TOS Enterprise is supposedly fun to fly and a bit better than the other starters, but everyone can get to the next tier of ships pretty quickly anyway, so it makes little difference long term.
- Instances have too little people in them. They should probably have made the game areas larger and have more people/instance in order to make it more lively but not too crowded.
- Not sure what otsego means with "the CORE is garbage", as I find the core works pretty good for a multiplayer game. Also, "nothing more than a mediocre space combat game with a Star Trek skin pasted on top"? I really can't agree; it may be a bit unpolished here and there, but it's a boatload of fun (which is the reason I play games), so I find it quite worth my time. Different preferences, perhaps?
Overall, the cooperative play fun factor, general lack of serious bugs (from my personal experience, it puts a lot of single player PC and "HD" console games to shame in this area), amount of general player freedom and a welcome lack of stupid cutscenes (or other forced situations where the player control is taken away to tell some "epic narrative") pulls it up to 8/10, or so. Together with games like TeeWorlds, New Super Mario Bros Wii and a few others, this game is quite far above all the junk released today in sheer entertainment (not that that's necessarily difficult).
Note: it is quite possible that someone else with differing opinions, expectations, hardware and/or software configurations will find the game more or less stable and/or fun. Take it for what it is, my (not so humble) opinion.
Edit: corrected a typo or two