I bought this to use as a practice pad and as a special effects pad to supplement an acustic drum set. I have a kick pad for a digital drum set that I hook up to the SamplePad for practicing rudiments, technique etc.
The SamplePad has a memory card slot which can be used to add custom samples and apart from the device being a bit picky with the sound formats this functionality works well. The sound quality, from a layman's point of view, is perfectly adequate, both for custom and built in sounds.
Handling the SamplePad is a bit fudgy and it takes a little while to get used to but once you've figured it out it is not a problem.
The quality of the device is average, the unit itself is plastic but seems to be able to take a beating. The big draw-down seems to be the software - it does not do well with fast strokes as some are missed and every now and then the unit does some sort of a reset - not sure if this is due to excessively hard hitting, static build up or a heat issue. Regardless I', not able to use it for practicing technique and/or speed.
The lasting impression, using it as a special effects add-on, is that I don't trust it, even though I have not had a problem with it in that application...