The 532 MB demo gives players a pretty good sample of the game, including a mission from the single-player campaign (which can also be played in co-op) and a multiplayer map. The demo also lets players create their own character to use in online matches.
Tom Clancy's Rainbow Six Lockdown has already appeared on consoles, with the 2005 release not going down too well with critics. This PC version isn't a simple port though, featuring altered missions, improved visuals, smarter AI and a number of multiplayer additions.
If you want to see if the changes made to the PC version have improved the overall quality of the game you can find plenty of download locations on the official Rainbow Six game website.