Like I said, my iPad is running define with iOS 8.1.1 on it. I will admit that things were a little hinky when iOS 8 came out. The first incremental update really didn't help much at all, but the most recent update to iOS 8.1.1 did the trick, if you choose to go that route, I wish you the same success that I am having and that the overwhelming majority of iOS 8 users are having.
You have to remember that this ASC forum is like a hospital where sick iPads come to be helped and cured of their ills. You aren't going to see many happy iPad users coming around here and shouting with glee, "I Love iOS 8, i Love iOS 8". They are busy getting on with whatever it is that they do and they are doing it quite successfully on their iPads.
If you decide to update, backup first. If you have been using iTunes, then use iTunes for the backup. If you have been using iCloud, then backup with iCloud. If you update with iTunes, the download is smaller and could take less time to update. Temporarily disable your firewall and antivirus software when updating using iTunes because those can interfere with the download. If you update with iCloud, make sure that the device is plugged into power because you don't want the battery to die in the middle of the whole thing.
OK - so in order.
Backup your iPad whichever way you choose. If you have been using iTunes that would be the way that I would recommend going.
Then click on the Restore iPad button - assuming that you are already connected to iTunes from the backup. You may be asked if you want to backup and you can do so again if you like.
You will get a message that the iPad is going to be erased ...are you sure that you want to do this .....etc., etc.
Say yes, to that option.
iTunes will erase then device and download and install the newest iOS.
After the update, iTunes will ask if you want to restore the backup to which you will say yes
After the backup is restored, iTunes will sync all of the content that you have chosen to sync, back to the iPad.