Well, I've been using the full (paid up) version of Opera 7.21 for 3 days now and I'm completely converted. It's just a better browser. It's faster, the tabbed pages are a pleasure and the mouse gestures are already almost instinctive. I like the interface, which is much more customisable then IE and is easy to live with. I probably won't use the email feature because I'm wedded to the PIM in Outlook 98 but I can see that it would work well.
It has it's little quirks and a couple of smaller features that I miss, but they are pretty minor in contrast to the advantages.
I'll stuff it in the Linux box (Konqueror's absence of word-wrap is too annoying - how could they have missed that?) but have no reason to suspect that it won't look and behave pretty identically.