If you own a Nokia phone before, N8 will be the right phone for you.
Actually, signed certificate is not the same as jailbreak. Signed certificate is very easy and will not harm your phone. I believe all Nokia user (smartphone) need to get their phone certificate key to install most downloaded app. Another way to install most app by not using certificate signing is firmware mod or jailbreak for *phone.

Hi, does anyone know what battery power saving actually do? I know it save battery usage but how? If I always put my N8 on power saving mode, will effect N8 normal function like phone call, sms and camera?