I use Opera on my PB as my default browser. I find it faster than Safari and with many more features. It has extensive security options that Safari doesn't although these can be a pain in exchange for the privacy. It has nice keyboard shortcuts, easier to manage pages and files etc.
It is indeed a wonderful browser, no doubt the best in practice of all. But, yes, one major drawback is that since it is WWW standards compliant not all pages work well, especially those specifically written for IE, like the bill pay sites. So, you will always need a second browser for those. Safari does pretty well from what I have seen but I never really know what is being put on my computer as I surf.
I have no problem paying for quality software, and Opera is one I have paid for.