Every single iPad upgrade has had problems.
In reality, most people upgrading don't see these problems, or don't notice them. But if you hang out on support forums, each upgrade comes with a huge spike in posts about problems; usually the same problems each time: battery, glitches, slowdowns.
You might go through three upgrades with no issues, and then get the upgrade from hell.
Many issues are temporary. Some so temporary that they sort themselves after a few days. When a new OS is installed it's often busy re-indexting and cleaning up stuff for the first several hours to a day. That's a lot of over head. A reset also helps.
This is the reality of computers today. Everything is so complex that it is impossible to get 100% reliability, especially with something as intrinsically risky as a major software upgrade.
So far this year, it has been relatively quite. iOS 7 was a nightmare of problems and complaints; mostly because a lot of people upgraded immediately, and with no idea how radical the changes would be.
This year has been quieter so far. I suspect it's because a lot of people are opting to wait for the first point update; or at least until they've heard how it's going for everyone else.
Android suffers the same early adopter issues; complicated by the fact that you might be working through several layers of changes instead of one, if you're not getting a pure Android/Nexus device. It's not worse, or not much worse, but it's not any better. At least not on the upgrade quality.
Android does avoid the 1st day server crush problems. But that's because they roll out updates over a period of time. You may wait up to a week for an update to become available on your device; while having to listen tot he smug 'I got mine' posts.
I have a Nexus 7, so I can keep up on what's going on in the Android world; so I have at least a casual familiarity with both sides.