Thank you for your post, and I apologize for the late reply.
I have an iPad 1 running iOS 5.0.1, and I do not have any issue with FileMaker Go 1.2.4. Could you provide a little more detail about your database files? For instance, do you have a lot of graphics on the Layout? Fields formatted for Checkboxes or Radio Buttons? Both of these will cause a slowdown in performance.
I know more than two months have passed, so if you have since found a resolution, please post here so others with similar symptoms can benefit.