Tom,
In backing up with Kevin is saying, the security issues with IE are legendary. With Firefox and Safari both, I have never seen a pop-up I didn't want. As far as the bells and whistles, well, I can honestly say I'm using all of them quite often. Auto Copy for instance. You hilight the text you want and it hits the "Apple"-"C" or "Ctrl"-"C" keys for you. I've got these plesant little icons below which contain the weather this very moment in La Habra, as well as the next 7 days or more if I want it. Tab Browsing, well frankly, I can't even think of not being able to operate the internet without it anymore!
It actually bugs me to see the IE "e" anywhere on my computer!
As far as download issues, I might be wrong here, but I have had nothing but trouble trying to download with IE. With Firefox, and especially with Down Them All!--a Firefox extension, it is faster then I have ever come across anything regardless of the connection being T1, Cable or DSL. Maybe an impossibility, but I swear to you this thing is blazing fast.