For me, IE7 sits midway between Chrome (super-fast, but unreliable, crashes and mishandles a lot of javascript) and Firefox (stable and lots of features and add-ons, but loads up slow and heavy). I would use Chrome more extensively, since I value quick startup times more than the plethora of add-ins, but it's not nearly reliable enough. IE is a good balance for me.
IE8b2 can replace it well, but it needs a lot of work on stablity and proper rendering bugs. I hope b3 or rc1, whichever is released, addresses those.