Ovi Maps is a huge battery drain for me. Especially if the phone is overclocked, the battery is drained in 2hrs.

I feel the phone is not responsive enough at anything less than 1GHz, but the battery life sucks big time at that clock speed.

IMHO the battery drain is also has some amount of randomness to it. Somedays the battery drains much slower than other days, in the same usage scenario.
Maybe it's some kind of placebo effect.