For me (Windows Mobile developer) the WM plugin is indespensible. I simply couldn't manage without it now. That's not to say that it's perfect, however...
Here are a few for the wish list:
I love the RAPI shell execute functionality, where you can launch a .exe on the remote device simply by double-clicking in SS. A great enhancement would be to make it also launch associated files - e.g. CAB files get launched with wceload, etc.
A remote registry editor
A remote task viewer - would save me having to load eVC!
The remote file viewer doesn't always detect changes to files. If you open a file with F3, change the file on the device and hit F3 again, you get the old version loaded from cache
Unzip files directly to the WM plugin - useful, but not vital
I'll second that the mobile device/activesync plugin is really cool, and I love it - and I would love to some of those features implemented in Salamander.
Although, I would have to say that I wouldn't put them under that high priority, compared to other features...
But the main thing that I think could be improved in the "Mobile Device" plugin - background transfers. I hate to see my Salamander being hijacked for an hour while copying large files...
Another annoyance related to the windows mobile plugin is that it can lose connection, and then one has to kill the Salamander process alltogether to recover...
(the windows mobile plugin get locked up in some infinite loop of message boxes...)
- maybe I should submit this as a bug report instead...