I've just had a wee look at your library and I really like the look of it. I was trying, and failing miserably, to make my own library when my brother suggested I check sfml out and it's great.
The one thing which i think my library did well though was the input handling. Instead of the traditional "while (GetEvents(&event)) {switch (event.type)...}" type thing, you just registered a slot in your initialisation code, and then call "HandleEvents()" and all the signals are emitted.
Is there any chance of anything like this in sfml. IMO it is a much more elegant way of handling events. Boost.Signals is a very nice sig slot library