I have used Internet Explorer since its inception, mainly because it came free with every computer I've bought. However, lately it seems there's been a bug which puts computers at a high risk from hackers, and since I operate my bank accounts online, I switched to Firefox for safety.
It's pretty good, but it takes a bit of getting used to. For one thing it seems to need plugins installed for all the things I took for granted - flash video, etc - and it'll take a while to sort all that out.
It is faster, but then I haven't yet bogged it down with a cache I rarely clear and massive amounts of cached pages I never bother to wipe.
All the same, if you bank or shop online, it might be better not to do it through Internet Explorer until that security thing is fixed.