I've used 2.1, owains 2.2 & 2.3, slades 2.2 and 2.3.... and they are all pretty similar in battery usage.
Everything set to OFF (wifi, 3g, data, bluetooth, screen very low, no active widgets etc)... the best i could get was 5% battery use per HOUR... rising to 10%+ when having anything enabled.
After reading about iOS, WP7 and Android tracking and logging position data, i decided to turn off the basic 'use wireless networks' in location settings.
Now (using a Deji 3rd party battery -which reports as a 1200mah battery), I get 3+ days with the same settings. Roughly 1% per hour when idle now.