This is the camp in the Mara we stayed in for second part of the Kenya trip - it was originally set up by Paul Goldstein who is a wildlife photographer and works for Exodus:
+10 for Kicheche. Book direct with them and just stay there for a week. We travelled around for three weeks and stayed in some pretty swanky places, but the constant travelling became a drag, and the simplicity and authenticity of the experience at Kicheche was the best.
Don't try to pack too much in - the guides want to show you as much as possible, but it ends up being a whirlwind tour. The best day we spent was when, despite the protestations of our guide, we spent a whole day just following one family of Cheetahs and just chilling out when they did, watching them patiently hunt, and playing together - magic!