If you are looking for the old-school fun that Quake 3 bought or you like good and fast shooters you need to check it!
It has amazing graphics and good sound. When you first get yourself into the game you are immediately transferred to a futuristic sci-fi universe. Everything in its world is on the right place. The game is quite addictive and you won't notice when those four hours of fun have passed.
It uses a good free-to-play model, something similar to the one that League of Legends uses. If you want to make your character look shinier you can consider buying skins (you buy them with real money), if you advance faster you can buy boost packs and etc.. It is a good model and there is no dis-balance. You can also buy things using XP points (the points you earn after every match) and buy weapons, weapon upgrades, armour upgrades, perks and other things to customize your character.
But as every game Tribes has its cons which are not many. The first thing is that on some setups the game doesn't load fast, but when you play it feels perfect. Another one is that from time to time you could experience some crashes i.e. sometimes when you minimize the game, but it's not that common.
As a whole I would definitely recommend Tribes Ascend to people who want to experience the thrill. Tribes is fast, great looking and requires some skill. As a free-to-play sci-fi shooter with jet-packs you won't find anything even close to this!