Don't think it has a huge graphics requirement at all.
Instead of the three classes (light/medium/heavy), which were all swappable a la Tribes 2, they currently have 3 light/3 medium/3 heavy sets, each with their own unique equipment sets that can be swapped around. That said, unlocking things like secondary weapons and whatnot is going to take you forever and a day without actually becoming a VIP member (i.e, supporting the game by paying real money towards it). It's possible, mind you, but some of the weapons cost 100k... and you might get 2k a win, less for a loss. VIP membership (paying any money at all toward the game) doubles XP for X amount of time, and the more money you pay, the more in game gold you have to unlock stuff.
Personally, because I know me and playing Tribes, I had no problem shelling out money to unlock a bunch of stuff - $40 pretty much got me all of the big, oh dear God that'll take forever to unlock. The other stuff I don't have yet, gives me something to work toward, since they tend to max out at 18k.
As for how fun the game is... well. I'd been wondering what I was going to do over Spring Break. This's pretty much been it.
From what I've been given to understand, they'll be adding in more maps, more armor sets, and custom servers as things really get going.
Currently, armor sets are:
Pathfinder - fast, agile, light spinfuser, often used as flag cappers/chasers
Sentinel - Sniper and base defense
Infiltrator - Stealth, no instant kill melee anymore, but have very powerful sticky grenades, good for taking down enemy base defenses
Soldier - jack of all trades, normal spinfuser, decent for pretty much whatever you want
Raider - two great packs, one that allows you to use your energy as a shield, one that jams enemy stealth and prevents your 'enemy icon' from showing up on someone's HUD
Technician - Base defense, can put down turrets, motion sensors, ect.
Juggernaut - Mortar/MIRV, heavier version of the spinfuser - long range bombardment of enemy defenses
Doombringer - Missile Launcher, chain gun, can put down force fields - good for base defense
Brute - straight up close range heavy - have fractal grenades that tend to be pretty effective vs. mediums/lights
That's just a quick skim though - all classes have a primary that can usually be swapped out for different primary, a secondary with the same, packs with the same, grenades/deployables... two perks each...
Gah. I have to keep myself from playing more. I've played too much the past few days.