My wife is still on 5.0. She rarely updates her apps also, but I do that for her when she gets around 20. I will update her phone soon sometime when she isn't using it.
There is nothing much to upgrade from 5.0 to 5.1 as there aren't that many significant changes or new features. Of course the update states the fix to the battery issue but it's too early to tell but from what I can tell from mine is that it's the same as before (never had the battery drain issue).
If you are satisfied with your 5.0 then I'd stick to 5.0.
I was still on 5.0 on my 4s until I upgraded to 5.1 on Wednesday. My battery had seemingly just started to last no time, so I upgraded to try to fix that. It's still too early to know if it helped.