Opera wants to know what features web developers would most like to see. I posted this in response (but it never seemed to show up on the page):
“Testing” version: offer devs a download pre-configured for more easily testing site compatibility with Opera. Marketshare will only rise if more sites are tested in Opera, so this has to be dead-easy for devs used to testing in IE/FF.
Strict-mode JS Notices: tell devs when they’ve attempted to use a common interface that IE/FF supports but Opera doesn’t. Link to a knowledgebase article, which leads me to…
Documentation: Be public and upfront about lack of support for popular proprietary features that IE/FF support and that web devs are itching to use, and list practical alternatives and workarounds in knowledgebase articles. In fact, publish usable compatibility scripts if possible, not just secret browser.js fixes.
In the 7.5 days this would’ve been XMLHTTPRequest. Yes, Opera devs were working on it, but web devs were in the cold for knowledge of the current level of support (eg. you couldn’t POST until 7.6 so many sites half worked). If support is in the works, let us know how it’s coming along! Not just in an odd hint drop on the forums.
This also goes for Opera-specific tech; I shouldn’t have to figure out myself that UserJS doesn’t fire in panels (why not?) or search forums for the most basic widget methods. Devs need thorough docs. Take the PHP docs as a model.
JS Panel: I sorely miss not being able to watch JS errors in real-time in a panel, as I did with v8. In fact, it should be a top-notch panel developed by Opera that ships with the browser.
DOM Inspector: devs love them, plenty of bookmarklet versions exist out there. Grab the best, improve the hell out of it and ship it in a panel or publish it as an official Opera bookmarklet. Grab one of your widget developers for two days and you’ll have this.