On my Windows machine -- I typically test different versions of Internet Explorer using an array of Virtual Machine instances (which obviously requires a fair amount of investme
No, I would not rely on it - at least not completely (i.e. use it just for quick IE tests, but still retest everything later in a reliable solution).
There are differences when testing both with IETester and IECollection, most notably in Javascript processing.
See a similar thread here: https://superuser.com/questions/118069/whats-the-easiest-way-to-install-multiple-versions-of-ie-and-firefox-on-the-same/
From the few answers there, the most viable solutions are virtual machines (which you are using already), or web services which do the testing for you (although these might not be suitable for everyone, i.e. due to data confidentiality).