I like thousands of Bolts search feature. It is one of the most encompassing search features.
The only problem I see with that sites search function is it is not proment and can be easliy over looked. I also like the color matching function. It has kept me from a few mistakes... I use it if I am not quite sure what the color really is , I get a nice isolated little cube of the color.
I do like your search by theme feature, It gets me quickly to the fabrics I want to pick from for a project.