Online co-op play can be tremendous fun.
Because they're mostly linear and because your squad now operates pretty much autonomously, the missions don't require a whole lot of tactical thought. However, the realistic damage and aiming model are still intact. You're vastly outnumbered, so you'll at least need to approach each mission methodically, moving from cover to cover while keeping an eye out for enemies hidden in the trees. Simply running toward a single enemy while indiscriminately spraying bullets will get you killed in a big hurry. Unlike a lot of recent squad-based shooters, your teammates can take damage and die (though, unlike the original, they don't gain anything for surviving), which adds an extra layer of tension to the single-player experience. You can save at any point, though, so if you don't want to continue minus one friendly, you can simply reload a recent save. The load times are surprisingly quick, especially considering how big most of the levels are.
Most of the missions are set in some kind of jungle, though a few take place in urban environments. The visuals for these environments are markedly improved from the original. There's a lot more foliage, and it looks and moves much more believably this time around. About the only visual disappointment are the enemy animations. Hostiles show little reaction to being shot. When dropped, they look less like they've been rocked by a forceful blow and more like they've simply decided to gently lie down and take a nap. Sound effects, on the other hand, are great. The ambient sounds of battle are forceful and varied, and they add a real sense of chaotic danger to the firefights.
All but three of the single-player missions (there are three missions in the campaign where you're not accompanied by your squad) can be played cooperatively with up to four people split-screen, through system link, or over Xbox Live. The cooperative mode, especially over Live, is a blast and it's worth the price of admission by itself. You can also set up several variations on the single-player missions in which you must infiltrate points on the map armed only with a silenced pistol, kill every enemy, or defend a position for 10 minutes.
Ghost Recon 2 is a departure from its predecessor, but dramatically improves on it in some important ways.
The competitive multiplayer modes are great as well. Five basic modes are available: domination (a capture-and-hold variant), hamburger hill (king of the hill), various flavors of deathmatch, search and rescue (each team tries to escort wandering medics back to their base), and siege (one team defends an area while the other team attempts to infiltrate it). There are a huge number of available options to tweak within each of these games as well. Permanent clans (called "teams") are supported, as is the creation of official team competitions. It's obvious that the developers put a lot of thought into implementing the online component, and it's nearly as fully featured as the current high watermark set by Halo 2. In fact, the jungle setting and the methodical, realistic gameplay actually make it more of a complement to Halo 2's fast-paced action rather than a direct competitor.
Though Ghost Recon purists may find a lot to complain about in the sequel's entertaining but admittedly relatively shallow single-player campaign, they should ultimately be mollified by the terrific multiplayer game. It hasn't been "dumbed down," but rather improved in every conceivable way.