Should I download this to replace FF and Opera? Nah, If it's not broken... Windows XP wasn't broken either.
I feel the same.
Making IE9 win7 dependent could prove to be the worse decision Microsoft has ever made. They are simply, willingly, handing over power to Chrome, FF and Opera which have no problem whatsoever running on XP.
A very stupid decision which Microsoft are going to regret (and Google are probably going to LOVE).