For a mid-ranged player like me this game can swing up and down. When playing on clan servers or ones with people who have been playing since the games start it's definitely rough because of the high level of skill that the people obtain for playing the game for 3-4 years. I love the different mods of the game. Gun game is an awesome mod where you progressively gain better guns and then the classic scrims against other clans or players is fun too.
Counter-strike source is amazing for anyone who likes online fps. The graphics are relatively great for an online fps, and the game can range from "owning noobs" in a pub match to actually using strategy and skill in high level competition. I love the game, but after playing for a long time you can hit a point where everybody better than you just destroys you. One concern as with any online game is the use of hacks. Steam prevents hacks with its VAC system. There are very few false positives with the VAC system, but there are some hacks that get through the net.
A great online FPS game, well deserved.