Personally i used activesync to backup all of my contacts and calendar, as unless you have them saved to your sim card they will be lost. As for the rest I just lost it all and reinstalled everything, but it only took an hour anyways. Anything on the storage card isnt lost, but any programs you have unstalled on *** storage card will remain there but wont work after the update, so will need manually removing.
The performace increase over my old verion (1.34) is mental, its really much much faster now, and a lot more responsive to everything. My wireless signal strength seems to have improved too as it used to say low signal and constantly drop out, now its at 75% strength.
I really cant stress how much faster it is than the old ROM that came with the phone. However, reports are saying its still slower than a lot of the cooked ROMs that are out there, so if ayone if running an update such as Duttys I wouldnt bother with this update, unless you want your warranty back