Well as far as the cost of this thing, you cant beat opensource and just the cost of the components. The firmware, circuit, and board files are all there for the taking, so probably wont find a better deal than that if you can produce your own boards.
That controller looks like it has just about all the features of a stepper driver one could want at the hobby level. Microstepping is a buzz word for these things meaning that they can exceed the typical resolution of 200 steps/rotation of a stepper motor using a control method they call "old school linear microstepping"(he claims it will do 3600 steps/rev). Looks like it will work with several popular CNC programs as well.
It is a Linear driver meaning that it linearly regulates the power, thus dumping excess power in the form of heat. So you will need a pretty stout heat sink. I see in the comments that people had used "Chopper drivers" which is a non linear method of regulation, however they reported that the choppers still produced a lot of heat on motors which to me sounds worse then having it done linearly and getting heat where you can deal with it rather then in the motors. I am sure that there are choppers that do a nice job and dont get the motors hot, but probably not at the hobby level.
It is a unipolar driver meaning that you dont need to reverse the direction of you current flow through the coils, wich makes for a simplier design, using a single mosfet switch to drive each side of the coils. Where as a bipolar stepper would employ an h-bridge driver which makes for a slightly more complicated scheme to understand as well as a bit more expensive.
All in all I would highly recommend getting/building this kit as you will learn much more about how these type of drivers work rather then a plug in play system where you dont understand what is happening. Whats the fun in that?
I am no expert in stepper motors, I know enough about them to understand most of the technical talk and what I wasnt sure about was easily answered by wikipedia:
http://en.wikipedia.org/wiki/Stepper_motor
