When you start with AJAX and sharepoint 2007 webpart after the year 2007, then it can be pretty daunting because most of the information out there on combining AJAX with Sharepoint 2007 was written in 2007 (end even before that in 2006).
This information is no longer applicable because Sharepoint 2007 SP1 supports AJAX. Sure you still have to modify a couple of things such as the web.config etc. (check my previous posts for a list of checks).
There are hundreds of websites out there that want to teach you how to use AJAX with Sharepoint 2007. Hell there are even several websites that want to teach you how to use AJAX with Sharepoint 2007 BETA!!!. People should surely take more responsibility for these posts and UPDATE or DELETE them when they are no longer applicable. Unfortunately this does not happen.
So let me tell you now that next time you google for information on how to do anything AJAX-related in sharepoint 2007 SP1, do yourself a favour and filter for articles written AFTER January 2008.
So you can safely ignore all those EnsureUpdatePanelFix() and similar pieces of code. Also you can safely ignore BaseWebPart and all other third-party webparts especially designed for ajax use in sharepoint. Using them will just give you more trouble than what its worth.