My company has recently announced that it has ended support for IE7. Lets all be thankful for that. Ever since I started testing web applications, I have had one heuristic that has served me well:
'If it is going to break, it will break in IEx' - the x was originally IE6, then IE7 and now it is IE8.
The sad thing is, I actually like IE. I preferred the interfaces of 6, 7 and 8 to the minimalist style of Chrome, FF4+ and now IE9. I have used it for years, meaning I had little trouble in finding settings, since I knew the general menu layout as well as the terminology it uses.
But the fact remains that, unless I have specific reason to use another browser for testing, I have to use IE8 because any problems that are in the software that are browser related, are likely to be caused by IE incompatibility than anything else.