As a novice i re-flashed my N900 and it transformed the device, which has become a nightmare after PR1.1.

It was easy, yook less than 30mins and all applicatiosn re-installed without problem.

The only issue i had was that the flasher would not work with my version of Win7 64 but worked fine on Win7 32. However I did have to restart my PC and press F8 and enable the Windows option that enables unsigned drivers IIRC.

This was a week ago and only had 2 re-boots and battery life is fantastic.

So long as you back up all will be fine.