personal preference really,IE7 is certainly alot better/faster than of old,particularly with the IE7pro add on. I personally prefer firefox and have the ie addon if a site is only available in ie. you can have both,no need to have one or the other have a play around see which you prefer.
I use IE7 for the same reason as Totally-braindead stated above. I used to use F/F and I found to be troublesome and got rid of it. I switched to Opera and found it to be more to my liking. Why not try Opera, you might like it. J.B.