Yep, having the same problem. I use iPad first generation with iOS 5.0.1, it freezes and I have to re-start my iPad quite often. It's different apps that freeze, not the same app every time.
I bought a new iPad 2 for my daughter as a christmas gift, it run well – until I upgraded it to iOS 5.0.1. Now that one freezes too! It's frustrating, especially for my daughter who's so happy about her new iPad 2 and can't use it without the apps keep freezing. This morning she asked me why on earth I bought her this iPad 2 when it's not working, she have to restart it quite often.
Same thing with my iPhone 3GS, use iOS 5.0.1 in that one too. It all started as soon as I got the iOS 5.0.1 inside. Sometimes I can't make a simple phone call since my phonebook freezes. I tap and I tap but nothing happen. So I have to restart my iPhone and then I'm able to make my phone call. And everyone knows that iPhone is not starting up fast either. What if my house is on fire? Well, before I can call the fire department I have to restart my iPhone!! I don't trust my iPhone because the phonebook freeze.
I'm a Macaholic, I use Apple products everywhere and anytime on a daily basis since years. But Apple products is not what they once were – without so many problems as I experiencing them today.
I really do hope Apple solve this problem with iOS 5.1!! 😢