Yes my iPad has been running very slow as of late and would like to reinstall the OS. I'm currently not able to download any new versions of iOS as I have reached my download limit for this month. I do however still have iOS 4.3.3 on my computer from when I upgraded to that version. Is it possible to do this?
Before you reinstall the iOS, perhaps you would be better off restoring the iPad - or eliminating some apps that may be causing the iPad to run "slowly". I did this myself very recently - restored to factory settings - then restored to my backup - Still had some issues and then starting removing some apps until I found the ones that seemed to be causing problems - and now everything is back to normal for me..
If you have apps that store a lot of data - some game apps can be offenders - maybe newspaper or magazine apps where the issues build up over time (I'm not that familiar with how these apps store data) you might eliminate the problem that way.
The iOS should handle any memory issues on its own for apps that may be running in the background so there is usually no reason to close apps in the task bar - but there may be an app that is running that could be causing you problems. If you want to close apps go to the home screen, double tap the home button to bring up the task bar, tap and hold down on any icon in the task bar until they all "wiggle", then tap the minus signs to close the apps.
You could also try a reset and see if that helps - hold down on the sleep and home buttons at the same time until the Apple logo appears - ignore the red slider - let go of the buttons. Takes about 10-15 seconds.