I got +55 Elo over Rybka 3 in 160 bullet (1') games. Maybe a bit below expectations, but perhaps the final version will be significantly stronger, and it may be that R4 scales better with more time than R3.

My quick impression is that r4 is modestly faster and with very different eval. I'm busy with the imminent release of Komodo 1.1, which should be about 20 Elo stronger than Komodo 1 and with Multi-pv and searchmoves added.