Well, try kernel-power 49 (from extras-devel), it is rock stable on most of the devices using dsp profile (250-805 with SmartReflex on). And should give you above 50% more battery life compared to stock kernel (depends on the usage pattern, your mileage may vary)

I am using my n900 overclocked to 900 since March 2010, no problems so far. Since KP 49 has been out I am using dsp profile with limits 125-805, rock stable.

And don't use helper programs for overclocking, all of them are CPU/memory intensive and will drain your battery very fast. Read the wiki article on howto overclock (a little outdated but still valid in most of its part) if you find dsp profile is not stable for you.

Don't worry that kernel-power 49 is in extras-devel, there is an old bug in repos preventing it from entering testing and extras. Just enable extras-devel, install kernel-power and kernel-power-settings from there and disable it again, without updating stuff.


Anyway, don't seek consensus on overclocking, you won't find one here

@eight - I don't want to sound offensive, but judging from your join date, number of posts and software you are recommending I don't think you are the one to give advices on howto overclock n900.


EDIT:
and don't install Karam's stuff, it is also known as crappatch