This game was AMAZING when it came out. I played the beta and got a new video card to play this back in 2004 (before BF2 came out). Unfortunately it feels pretty clunky now and the main reason to play it is probably nostalgia. There are actually still some die hards and nostalgics who still play this and there's always 1 server with at least 30-40 people (usually playing the vanilla game which is missing some cool stuff that was in the expansion) and some other servers with just a few players. Also the Co-op mode was really popular and had entire clans based around it
Cool things this game had many of which were ahead of its time : 75v75 multiplayer on ridiculously huge maps (much bigger than Planetside 2). There were servers with like 50+ capture points where the battle would rage for days on end on archipelagos with hundreds of islands. It had iron sights, lean, prone stances, class-based customizable loadouts, actual grass you can crawl and hide in to flank and snipe and some dense forest environments, vehicles that require 3+ people to crew, massive transport helicopters that can load light vehicles, hovercraft that can transport tank, light transport and attack helicopters, parachutes, sniper rifles with adjustable zoom and elevation, all the weapons which are now staples in games like battlefield: Assault rifles, SMGs, LMGs, Sniper rifles, sidearm pistols and shotgun, RPG, Stinger, Javelin, C4, Mortar, tank mines, frag flash and smoke grenades, claymore, underbarrel grenades, equippable knife, medkit, body armor, selectable ammo type (ap sp, fmj). There is no sprint in this game (wasn't a standard feature in fps back then), but your move speed is based on the weight of the items and ammo you equip which was neat, so you could build super fast loadouts by dropping to minimal ammo and weapons or even drop everything for a knife commando loadout.