I think it will. It won't improve your max download speed, but it will improve how long it takes your system to display the page. IE6 had a lagging issue with highspeed internet, it wouldn't load pages at full speed. It seems that IE7 has fixed it though, but I don't know if your processing speed at dialup will change any.
I've been using IE7 for several months now and really like it. I was just introduced to firefox and i like that too. Not quite sure I'm 100% ready to drop IE just yet, but I keep finding more and more firefox add-ons and plug-ins that may just change my mind real soon.