Edward,
I tend to upgrade "everything" anytime infragistics releases something new and every once in a blue moon I will find some little bug that I need to fix but for the most part it is pretty small change. What I do is install the new infragistics version and run the upgrade utility and then open my folder and delete all the previous infragistics dll files from my bin folder and then copy the new "upgraded" dll files into my bin directory. I don't use the GAC with a reference to the dll inside web.config as it produces nothing but problems so dll controls I tend to just drop in the bin directory and read locally which has made upgrading extremly easy.

Now on 2008 v1 from 2007 v3 went perfectly except for the "Infragistics.Excel" which seems now to be "Infragistics.WebUI.UltraWebGrid.ExcelExport" but have been to swamped with personal stuff to jump in and change the "Workbook" code from my 2007 to 2008 upgrade yet, there are also some slight changes to the css files for appstylists but all in all (minus the excel stuff) it was a pretty smooth transistion.

The upgrade from 2006 to 2007 was painless however I do not use design mode for anything so from your links above I am not sure why you would be experiencing those problems other than having a old dll hanging around in your bin file or a reference to it in your web.config file.

Thanks, Chris.

I'm going to take another stab at it in a couple of months.  Our app is just to big to upgrade often; last time, when we went to 6.3 from something a good bit older, it proved quite painful.  (Or so I'm told by the nay-sayers around here.  ;-)