Hrmmm...
I could make it hard...then again you can also make it easy.
Take a good hard look at how shaders work and spend some time learning how to optimize them. Clean code runs much better than sloppy code...even when it is going through the GPU.
Other than that - bumpmapping can be very taxing when you have a lot of lights in the scene and a lot of texture space to be transformed. There are a lot of tricks invloved in the performance tweaking aspects (enough to fill an entire shelf of my library and then some). Read up and try it out - getting the desired shader working is easy - getting it to work efficiently is the tricky part.
Also - combine shaders where you can...you can get away with using a bump shader than following with others - it will run faster when it is a single process.