I won't be leaving Opera anytime soon.
I was just checking out IE8, and it's not for me.
Can I customize the right click menus? No.
Can I move things around to my liking? No.
Does it have a built-in email client? No.
Can I add custom buttons, and functions? No.
Does it have a password manager that compares to Opera? No.
Can I get to site preferences with a simple right click? No.
Does it have "Paste and Go"? No.
For these and quite a few other reasons, I'll stick with Opera.