In spite of all the benefits of computer based music making, there's something to be said for the feel of a fader under your fingertips or of twisting knobs and pushing buttons. We jsut love being in total control, which is why Midi controllers have become so popular in todays market.
For all those people out there with soft synths and samplers that are just dying to feel their music, thisis a chance to do it for a fraction of the price of the hardware equivalent.
If you have already got some software, try and find a contoller that has been specificallly designed for that piece of software. For example the Houston works amazingly with any steinberg product. If you haven't decided on the software then maybe the controller you buy may will help.