I said it elsewhere. It's better, but not really decent.
Browsing is improved. Typing anything or opening an app feels like a time machine.
...ok, so iOS 8.1.1 is marginally better than 8.1 but not by that much!! I still get noticeable lag when typing in Safari (not as bad as before but it is still there), also, stutter is still present (again, not as bad as before but its still there) when opening and closing apps (the 'zoom' animation still slightly stutters when you tap on a folder to open it).
I have found, however, that it vastly improves the speed on the iPad 2 if I turn off the 'Transparency' and also the 'Reduce Motion' features, both which can be found in the 'Accessibility' section. Have also turned off 'Background Refresh', which has also helped. Looks wise, its not as pretty to look at but I can take that hit if it improves the overall performance of my iPad 2 - which it has!