Thank you for your question. I'll do my best to assist you.
It's not only you who are experiencing that issue. A lot of people who updated their Apple devices (mostly iPad 1, iPhone 3GS and iPod touch) to iOS 5 made the performance of their device to slow down specially when it comes to data connection. I think it is because the iOS 5 is mainly configured to run on A5 processor that is available on iPhone 4S and iPad 2.
Unfortunately, Apple does not support down grading to previous version. But what I can probably suggest for now is to wait for another update that will fix this problem which Apple normally do. I'm not just sure when will it be but I'm pretty sure that Apple will or maybe working on that already.
I may not able to help you to fix the problem with your iPad but I hope this answers your question. If it does, please click the Accept Answer button below the answer. You must be logged in to see this button. If you have any follow-up questions, please post your comments below this answer.
Thanks again.
Glenn