In a bid to get rid of cheating on Rainbow Six, the latest patch has added in a "report button", you can now report a single player direct to Ubisoft for their consideration of banning them. Any suspicious behaviour can now be easily dealt with.
Also, Kill cams have been introduced in to ranked matches. Allowing players to see their own deaths and "grow as a player".
There are a full listing on the Ubisoft forums here:
Spawn points are also moving around on a lot of maps. Making it harder to kill players upon spawn out of windows. Ubisoft have moved them behind vehicles in many cases, moving them altogether in some cases. There are some lovely screenshots too, like the ones below on the link.