I am very curious to see how this works out. Gusev's talent is obvious--not only in the Classics, but also in time trials. If Katusha has a serious GC contender (still not convinced that Rodriguez, Kirchen, or Karpets are up to the task, though) then Gusev will be a tremendous addition as a super domestique. He can also win smaller stage races, potentially, with his tt strength and ability to handle varied terrain.
Katusha could be the perfect fit, too. I remember that early in his career CSC let him go--despite his talent--because he was a social misfit at CSC (very uncommunicative and never seemed to buy into the whole team concept that CSC was pushing so hard in '04-'05). Then, Gusev really came into his own at Discovery with some Russian leadership from Ekimov. Could be more of the same at Katusha.
Either way, I hope it doesn't take Gusev too long to find his legs again. He's been away for a while. And, I still want to know, what took so long after he was cleared to ride??