Just noticed the third beta of the Opera browser for Windows Mobile-based smartphones was released last week. It's been in public or semi-public beta for at least six months; not sure why they're taking so long to get the final release out.
This beta is still not as feature rich as the Series 60 version, but it's based on a much newer rendering engine and certainly performs well in terms of page loading speed. I think much of it's speed is due to built-in support for the Opera Mobile Accelerator proxy service. If I had to pick a favorite feature I'd say keypad shortcuts, but I really hope they add page tags and jump-to-text features from the Series 60 version.
While I'm certainly biased, I think the Internet Explorer browser included with all Windows Mobile-based smartphones generally provides a better user experience - up/down smoothly scrolls page and navigates links, don't have to double select form fields, no three-level-deep menus. I also like the flexibility of having three vs. two layout styles to choose from: single column, desktop, and default (resembles desktop with no horizontal scrolling). Opera's single column view just doesn't work great on all sites.
It will be interesting to see how strong demand for Opera on Windows Mobile is once the final release is out. I don't see very many people paying $29 (plus another $18/year for use of Opera Mobile Accelerator service) for a product that duplicates a built-in feature that works well and will only get better. Even at sub $1/unit OEM pricing (I have no idea what they really charge) I think it will be hard for them to prove the incremental value it adds. Or maybe I'm completely wrong.