Even if you had to pay for it (which you don't), it'd still be some of the best multiplayer you could ever get.
The game is old, and free, so anyone even slightly interested in it should be quite familiar with the gameplay. Teamwork with various classes and objectives. VERY good stuff, missed in pretty much any other multiplayer game.
The graphics were top-notch, but the graphics have poor compatability with multiple systems. I myself had to open up a config file and increase the amount of memory dedicated to the game so it would run faster, as it would normally run UNBELIEVABLY SLOW, even with all of the video and audio quality settings all the way down. You cannot increase the amount of memory dedicated to the game as an option in the game itself. It's rather obscure in that respect. Even after increasing the memory allocation to the game myself, the game still runs ridiculously slow in some parts (just SLIGHTLY faster than before).
The sound effects weren't all that great. The spoken dialogue is like idiotic broken English. Characters will only say key words of what they're trying to convey, like "Enemy in disguise!" if an enemy is in disguise. It's certainly effective, but it sounds stupid when an actual voice is saying it. The Germans speak English (like in the single player RTCW), but they randomly throw in German words for the heck of it.
Well, the need to manually set memory allocation, and the rather weird-sounding dialogue and not-so-great sound effects don't put any damper on the amazing gameplay. I love being a medic, as I can contribute greatly to my team and be in the middle of a battle without my team relying entirely on my ability to kill others. Players can become stronger as they fight or perform class-specific actions like healing or repairing.
Your character becomes wounded upon running out of health, unless hit by an explosion, wherein they're blown apart. A wounded player can be revived by a medic, but the killer still gets a point, even if the person he "killed" is just revived on the spot. Wounded players can also be finished off.
The wounded animation is exactly the same for everyone, and everyone also dies in the same pose, so corpses are kind of annoying to look at, as they're all in the same position whether they were shot, hit by a nearby explosion, or stabbed repeatedly.
The game utterly lacks any authenticity in the department of weapon loadouts. The MP40 and Thompson are exact copies, as are some of the other American/German weapons. Rifles are only used for sniping or grenade launching, so the primary weapon of every class is a submachine gun. The American sniper rifle is just an M1 Garand with a scope slapped on. What the heck? The panzerfaust fires once, takes like an hour to recharge, and suddenly you have another panzerfaust.
Unrealism aside, like I already said, the gameplay is just awesome. Not only can it be addictive for lovers of first-person shooters, multiplayer and teamwork, but it's ABSOLUTELY FREE, and it's even better than the first version, which came with the retail RTCW game.