I got the KWA KZ75 a couple weeks ago so I could practice things like drawing, target transition, etc in the basement. It works pretty well. It has gas blow back, so there's a little bit of "recoil" but its less than that of a 22LR Kadet. The weight is also less than a Kadet. Definitely weighs less than my Shadow, but I didn't put it on a scale to measure the difference.
Overall, I think it has helped my shooting, its fun, and its cheap. You can buy 5000 bb's for $10.
Let me know if you have any specific questions, and I'll try to answer.