Hi moritzhberg, yes it seems like having a clean, or near clean install of the earlier OS is a key part of iOS 8.1 install success. For me my fall-back plan - if you can call it that - was to blow the iPad away to factory settings and install 8.1 as a fresh install. After all, that's what I'd had to do a few weeks back to get 7.1.2 back onto my machine, when I'd discovered that my backup was no good, and I couldn't go back! I'd done it once, I figured I could do it again. There was nothing on my iPad in terms of documents, photos, settings that I could not reconstruct from elsewhere.
With regard to Safari, I must admit for better or for worse, as with my desktop, I tend to use Chrome on the iPad, and that seems to be working pretty well.
When I did try to use Safari for example to access this site, as I use a password manager, and I was trying to paste in the password into the password field from my password manager, Safari certainly didn't behave as neatly as Chrome in terms of accepting my tap gesture to get the "Paste" chiclet up in the password field. I'm not sure what is the cause of this, but it seemed to work much more reliably in Chrome.
As I said, there is a general perceptible performance hit across the board on the iPad under 8.1, but it does't seem as massive - unusably massive - as I perceived it to be with iOS 8.0 on the iPad 2.
For me with that original release there were two key factors that made me believe it was a no brainer to go back to 7.1.2 while I still could:
1. 3G kept dropping out
2. Performance of the "Gold" version of iOS 8 on iPad seemed totally performance mismatched / ill-tuned to the now admitted agieng iPad 2 Platform.
For those reasons I decided to hold off, but I must admit I was now up to at least 5 apps that no longer updated because they were now iOS 8 only so I knew I was going to have to move sometime. To date for me it looks like a good decision to have moved.
Cheers,
Trevor from Oak Park.