It is brilliant on the Mac, and is the browser on the iPhone and iPod Touch.
They first released it as a beta for windows and it was cr@p and probably put a lot of people off. When I tried it on a PC I was very disappointed. (Apparently) the flaws have been sorted for the proper release, and I have seen generally good if not glowing reviews of it
The proper (non beta) version has just been released for Windows. Here is a recent review.