I bought Texture maker while ago and like it and it's features a lot. What comes to making seamless textures it has it problems that all programs have (at least all I have tested) that it fits for some textures but if you have a lot of details in a texture it's basically useless and you have to make them by hand anyway.
I'm eagerly waiting to see what improvements you have planned!
Btw. bump mapping (when it's available) would be great thing to see in your level geometry.