TheJadedMieu: Limitations:
1. You can only select from a short list of games
2. You only get one game at a time for free, you can buy more slots
3. There's some sort of cooldown when you remove a game from a slot
Immoli: For number 3, I believe the cooldown is for after you put a game in the slot, not after you remove it.
Indeed for # 3 there is a 14 day wait from the time you put a game into the slot. Your first choice is covered by "Newbie Protection [on which there is no FAQ available, though a link tries to point to one]" meaning you can get a free instant slot removal once.
The ads aren't much of an intrusion, I don't see them being added to the games themselves because that would require software devs to do some major rewrites of game code. The way it works now is the ad player "hooks" into the launch process of the game executable [where normal DRM check would be, making me think that the DRM check calls a modified DLL function that, instead of checking normal authentication, plays ads]. You can see this by paying attention when launching the game, the ads will play then briefly the desktop will be shown before the game loads [on fast systems you may not notice anything].
My only quibbles are that a) the ads are way out of date [Cataclysm ad keeps showing up for me], and b) no volume regulation between ads [one for Gods Online always plays at max volume which is quite annoying]