That's interesting. I just had a whole discussion on the forum about the sharpen filter. I use it too, but I was wondering if it is possible to get a painting this sharp without using the filter. Using it feels like I didn't do a good job in the first place.
I really like the seeming simplicity of this piece. There are no fine-line details, and yet it feels like small details keep popping up out of the background of this image. I really am in love with it for a multitude of reasons. Excellent job.