Unique features will include: OS independance/Multiple Styles/Multi-Language Support.
Coding will be in C++ using the Qt toolkit and will be entirely GPL.
The main goal of this client will be to not have to re-invent the wheel. I'm just curious what everyone feels is the best C++ implementation of the LJ protocol which has a license in which I can re-use and distribute the code under the GPL. XML-RPC is preferred because... well, let's face it, it's just cooler and for me I'm more used to handling data in some sort of XML format.