Mostly browsing (new Chrome works well), Netflix, LogMeIn Ignition for remote desktop, photo viewing, Skype.
Compared to my new MacBook Air it does seems a little slow starting apps, etc, but the thing is almost 2 1/2 years old, still has good battery life, and basically does everything I want. I think I've got my money's worth already, and expect to keep using it in the future. BTW, cost of those iOS upgrades - $0. Not a bad deal compared to the $50 that software like Parallels keeps asking for every year.
I have an iPad 1 myself, and I am looking to replace it.
Browsing - complex pages (techcrunch is one particular abomination) have a tendency to crash Safari. Chrome was far too slow to bother with.
Old Twitter app was crashing several times when loading in-app browser.
Applications in general tend to quit a lot.
It worked wonderfully when it was out, but its barely usable now.
Since iOS 5 my iPad 1 has been utterly unusable - many multi second lags and endless application quits.
Even brand new out of the box the iPad 1 and also the original iPhone were incredibly unstable - particularly in safari.
Everyone turned a blind eye to it.