Have sketchbook design myself,never got into it because I hate how awkward the interface is but these really turned out neat.Might consider getting back into it.
It deffinatly takes a while to get used to the UI since it's more loaded then Sketchbook Pro. It's still a damn good program to use for vector drawing. I'd prefer it to the pen tool in Photoshop, though, the painting and brush tools in designer are still a tad limited for my liking. Guess those are good reasons to use both programs together I suppose.