I'm on the closed beta, but thankfully there's no NDA :) So here's my mini review/preview/thing.. However I've been beaten to it and there are a few comprehensive previews out there already, so I'll embed one from youtube below as well.
I like it a lot. It's just like the old Tribes game and that is exactly what we would have hoped for, as the original is a classic that was way ahead of its time. Gameplay is exceptionally fast because you can move at insane speeds, using a technique known as skiing where you use downwards motion to skim across the ground and then combine this with your jet pack to go hurtling through the sky. I must say that it is an absolute joy just to move around in this game, the devs talk about "freedom of movement" and yeah, they've totally nailed it.
Most of the weapons have travel time to account for with their munitions, some being direct fire and others working like the classic mortar / grenade launcher style. This means you must learn to instinctively calculate lead time for your shots to have a chance of hitting those fast moving enemies. When it comes to a shooter being a game of "skill", Tribes remains unrivaled.
Tribes has always been built around Capture the Flag and Tribes: Ascend is no different. The maps work perfectly and features with bases and defenses that are actually worth something in game; the turrets are nasty... These bases also include equipment terminals and pads for summoning vehicles you can drive like tanks, bikes and a jet fighter. There are various classes in the games which change your weapon and equipment load outs, however you have to unlock these classes with XP or by buying them from the cashshop. Yes, Tribes: Ascend is going to be F2P with a cash shop and supposedly progress from beta is NOT going to be wiped at launch...
Though note this isn't a pay for power thing, it's very much pay for options that you can still earn without spending money. For example the Soldier, one of 2 starter classes that everyone gets, comes with the legendary Spinfusor. Which makes me go :) :) :) The Spinfusor is the iconic Tribes gun and once mastered is absolutely lethal. However it will take a LOT of time to unlock the other classes, but personally that doesn't bother me. If I choose to play the game totally free then I should be prepared for it to take time, otherwise nobody would use the cash shop, the developers would never make any money and F2P as a concept would fail.
Graphics are mostly good, but sometimes do look a bit basic compared with the latest flashy shooters. Yet I think that's mainly because the game needs very humped and often extremely fake feeling terrain to make the most of Tribes unique player movement. And to be honest you're flying about at such speed that really you quickly stop noticing.However it must be said that if you expect BF3 graphics and that's the most important thing for you, be warned that this is a game built primarily around gameplay and as such the graphics support that, not the other way around. IMHO this is a good thing.
I would definitely recommend people give Tribes: Ascend a try, it's shaping up to be a great game, but I would say if you've not played Tribes before then you must be prepared to get your arse kicked.
Finally, if you want to see a lot more game footage and a more comprehensive review, watch this chap's video below.