Please add support for the built in miner (start_mining and stop_mining commands in the cli wallet).
Many people who are not serious miners and don't want to figure out how to configure a pool can still solo mine in the regular wallet and help decentralize the network if it is as ease as a checkbox to turn on and off, with free coins occasionally being dropped into their wallet if they get lucky. A very successful coin could have millions of people doing this. This was Satoshi's original vision and unfortunately got lost in bitcoin but we can bring it back here. It is a game changer.
Your wish...

Update (
download):
- Payment ID can be entered in transfer tab.
- 'Send' button in transfer tab is not enabled while the GUI waits for confirmation or error from the wallet client.
- Solo mining support added.

Eh... that one is windows only as well, what happened with multi platform?
I must sadly say the linux/mac implementation will not come from me in the near future. I have put considarable effort in porting my .NET wallet to use GTK#. I got the program running on Ubuntu, but developping the GUI for GTK# (using monodevelop) was so clunky (crashes of the IDE, combined with corruption of the designer files) I decided to put my plans to port the program to mono/gtk# on hold for now.
The core of my implementation can run on mono without any modification. If someone would like to implement a different GUI which runs on linux and/or mac, I will be happy to assist.