As stable as IE (when it comes to memory leaks that make the app like a dinosaur), as fast as Firefox and as you all know its now FREE..
And i happen to like the integrated email application..
No more folders and shit.. just one inbox with a filter view.
Sorted by your own rule, active conversation (thread like) and by person.
Remind me a bit of how Gmail handles mail.
Wonder how that will do on larger quantity emails tho.
Try it out!
www.opera.com