What exactly are you trying to test? Simple html pages, java applets, flash, something else entirely? If you specify what exactly you are trying to test, others can provide you with more exact answers.
WR supports both IE & NN, we have tested the application on both the browsers it works fine. Again it is specific to my application prospect. If might not fit in your envirnment etc., So I would suggest do some pilot run and discover.
If you want a high quality software system, you must ensure each of its parts is of high quality. by Watts S. Humphrey