All in all, it's not a bad game, and I'd recommend it to anyone who likes TF2 but is sick of actually playing TF2. I don't know if I'll be playing it beyond the weekend though, $25 is a bit hard to justify when it feels like the game just isn't really complete.
I went ahead and bought it, since I can see myself having a lot more fun with the game, and I'm certainly not done with it. It's become more enjoyable as I've figured out how everything works.
For one thing, when you're playing single-player, and the game deserves props for actually giving some attention to single-player, the AI is trying to improve your game experience more than it's actually trying to win. The enemy team always seems a lot more competent than your own, but they can still fold. Meanwhile, the friendly AI expects you to always be the mission-critical class or player, and does a reasonable job of protecting you - if you try to hang back or run off sideways and let the AI figure it out, it'll flounder around a lot worse than the enemy AI does at exactly the same tasks.
I was originally miffed at the "selection" of weapons that are all functionally similar or useless, but as I've experimented, they are similar yes but not identical. Each weapon has it's own distinct character that stats don't really convey, and you come to pick some that subjectively feel better to you, even though they all work in essentially the same fashion. The last game I played with that dynamic - a "realistic" spread of guns that better serve to be picked by preference and feel than absolute advantage - was
Stalker, and it's not a bad design. I have two characters I switch between, and they use different stock weapons because I like the variety and strategy, beyond experimenting almost every match. Some weapons do benefit from mods so much as to be necessary, but almost all of the guns and useful mods can be unlocked in a couple hours of single-player, and none of the locked guns are game-changing.
Of course, some weapons are just plain useless - the grenade launchers come to mind. Only the Soldier's special Molotovs are really useful because they blow up on contact. As much emphasis as the game places on the tactics of grenades, it makes it equally easy for players to see grenades coming and get out of the way (and the AI is virtually immune to them). The shotguns try to break from gaming norms, but they wind up not really being useful at any range do to the funkiness with hitboxes and health differences. And melee has such a small hit range as to be pointless, not to mention you can't see anything for a second.
I'm still and always will be miffed about having to earn cosmetic effects, in a game that trumpets being able to define your character's looks (for what little good it does), but pointless customization of the player's image is a great enough goal in game design that I can pardon a lot for it. And like the weapons, a couple days of on and off single-player by an FPS chump like me unlocked almost everything. And since everything is common to all characters, there's no backfilling. Weirdly, I kinda dislike the character design aspect because it kinda kills any sense of immersion the game tried for (to the small extent that it does or needs to), because as cool as it is seeing different player looks, which really is great if you play with the same people so you recognize each other, it really reinforces the fact that you're two teams of immortals punting over objectives, because you keep killing the exact same unique dudes.
I both dislike and respect the character advancement system. Considering how easy it is to criticize what is ultimately a team deathmatch-maker FPS for allowing players to be straight-up better than each other by just playing longer, it's actually kinda bold that they stuck with the design. Like the classes themselves, the character advancement feels like it differentiates and specializes how you want to play and what you're best at, without fundamentally changing the game or making one player or another unbeatable in a given situation. They're all minor enough changes that they can't unbalance gameplay, but you can still feel them. It's a good dynamic, especially since even my casual amount of gaming in one weekend has earned me more experience on two characters than I know that to do with.
I guess what I'm saying is, I got my money's worth, and if you're into team-based shooters and want to play something besides TF2, it's worth a shot. I think the game has some balls just for trying to compete with TF2, especially since you get a hat for buying it (...that's pretty brilliant actually). They also deserve some props for making the game free to play temporarily, to promote their first DLC which is
free. I can't tell you how refreshing it is to see a game that gives you stuff without so much as mentioning "microtransations", and this is Bethesda we're talking about.