I generally am content with the stock browser. I've tried Opera as well.
Good about Opera:
1) It is very fast to download compared to the stock browser.
2) When you open the browser, it opens to a page of bookmarks, one of which is to the New York Times. They apparently have put some work in on the New York Times link, as it is complete, not seriously scrambled, and a fairly decent reading experience. You can add your own links to this opening page of bookmarks.
Bad about Opera:
1) Opera scrambles the layout of many sites, presumably due to the compression done to make for fast downloads. In a few cases, the scrambling moves past the annoying to making things into gibberish.
2) No pinching to zoom or expand the view. THIS IS A REAL PROBLEM FOR ME!
Thanks to the no-pinching problem, I use Opera to read the New York Times every day or two, but don't use it for much else.
I haven't tried many browsers beyond Opera and the stock browser.
By the way, I like this topic. One of my main uses for a smart phone, including my new EVO, has always been to browse the internet on the go. Clearly browsers are a big part of that.