I did the switch from P5E to Rampage yesterday, no problems at all with flashing the bios etc...
Everything works just fine, now I finally can read some voltages in windows, and a lot of ram tweaks came available in the bios, I LIKE !

Also my vdroop is lovely, I got with my Q6600 on 4Ghz idle 1.384Vcore, and load also 1.384Vcore ! Only the vdrop is 1.4000 set in bios and get 1.384, but I don't mind...

About the overvolting thing off the P5E, now I can read the voltages I can say the P5E overvolts the ram with 0.09, so if you set 2.2 you get 2.29 !

Hopes this a little bit helpfull .