I use opera across all my devices: Win7 PC, Android mobile, and ipad.

The desktop version offers some good security/privacy features that are not replicated on Mini or Mobile for either mobile OS. I think these would be very useful on the mobile clients:

1. Block third-party cookies. Mobile versions only have the option to block or accept all cookies.
2. Tap to Play (like Click to Play) to prevent unwanted flash videos loading and killing bandwidth.

Others may want more than that, but think these two would be a good start.

Thanks.