Opera has come a long way since the previous Macintosh versions, which I feel were all basically crap. 7.5 renders pages very fast, and very well could be the fastest browser on the Macintosh on this regard. It handles Unicode characters very well. It has wonderful HTML support, but I would say not the best CSS support. It renders the size of drop down menus quite a bit larger than other browsers and it looks odd on site that use them in their navigation bar. It also has some CSS shortcomings that are immediately obvious (both shown at kongming.net).

The user interface, I feel, is still cluttered, and the ads only make this ten times worse. They certainly have more a right to charge than the OmniWeb makers have (their browser is still poor, you can just use Safari), but I feel Firefox is still much better in features while Safari offers speed along with a decent featureset and similar stability when rendering pages. I would still easily choose either Firefox or Safari over this browser, and both happen to be ad free.