There is something I didn't get about the new WebKit-based Opera for Android.. It's now clearer. So in normal browsing mode, the rendering engine is WebKit. But in "mini" mode, the rendering engine, server-side, is still Presto, right? I don't think the teams had enough time to move to a WebKit-based server farm.
A while ago, SkyFire was a Gecko-based solution. Fellow mozillian Alex Vincent worked for them on that and I contracted for them too. But SkyFire switched to WebKit two years ago and they're a server-side browsing solution. So SkyFire was acquired for that. Well not only for that, but that's certainly a major point.
Until full integration of SkyFire into Opera's servers is achieved, users should probably expect browsing differences switching between "normal" and "mini" mode...