i turn it off and then on again at night just cause its almost like a computer and you shouldn't keep that on all time too.
Exactly my thoughts. Specially when installing tons of apps.
I have had serious User Interface issues lately on my non-3G iPhone:
Example:
a) Incoming call: The phone starts vibrating
b) I slide to Accept call
c) Slider gets stuck at the end
d) Phone keeps vibrating
e) Backlight goes off after 2-3 seconds
f) I touch the screen to bring on the backlight
g) Now there is no slide to accept (or slider stuck screen). Instead there is an in-call screen with End Call.
h) I end the call, as such the call time outs and goes to voicemail anyhow.
i) Bang !! Now I see the home screen with this Green Current Call bar on top "Touch to return to call" with a call timer
j) When I try to click/touch "Touch to return to call" it does a loop of coming back to the home screen animation and the "Touch to return to call" comes back.




....

I'm fine with it considering the fact that its so much useful to me. I can live with a bug or two.