With the Xiino [xiino3.4, xiinodead, xiinooffline] web browser offline, I decided to try Opera Mini 4 on my Treo 650. I'm a huge fan of Opera on the desktop, and despite its quirks, Opera Mini is a worthy handheld sibling.
Opera Mini is not a native Palm OS application. To use it, you need to download and install IBM's Java VM. Together, Opera and the JVM take up somewhere under 1.5MB, which is in line with other browsers. This lack of native Palm OS support leads to several issues:
Quirky non-Palm-like interface (press P to go back, Q to bookmark, 1 to open menu, etc)
Does not remember app state when switching between apps (must re-navigate to previously opened web sites)
No clipboard support, which makes it effectively impossible to transfer a URL from any Palm app (like Contacts or email)
Does not work as the "default web browser", which again, leads to non-existent integration with an email app
However, if you can get past the Java issues, Opera Mini is a fantastic browser:
Superb mobile proxy service, with very fast page loads and nicely scaled images
Excellent "Mobile View" mode that reformats pages for the small screen with nearly flawless formatting
Unbelievable "Full Page" mode with a virtual cursor - the page rendering is similar to Opera on the desktop
Excellent search integration with special box on the Start Page
Integrated RSS reader
Plays well with custom small fonts
Opera Mini also has a bookmark sync'ing feature, which I have not tried.
Other minor issues to consider:
Slightly slow startup time
Occasionally hangs (Palm Java VM issue?)
Tables could be formatted better in "Mobile View" mode (such as Yahoo Portfolio tables)
No URL helpers in the text entry boxes, such as shortcut buttons that automatically fill out "WWW." and ".COM"
Upon startup, it always seems to prompt you for permission to connect to the internet, and there is no way to set it to "always allow"
All in all, there is no comparison in the mobile web browser world. Opera Mini is the most impressive mobile browser I've tested yet on Palm OS (compared to Xiino, nWeb [nwebreview, nweb, nwebcache], Blazer, NetFront, WebPro, etc.) It is a shame that Opera is saddled with such a clumsy, non-standard UI and no real Palm OS integration. Opera could be, and should be, the standard browser for the platform.