I don't really think that you will improve with robots. If you have technical errors they will get worse but they are good to keep some speed and ball feeling
I have a Robopong 2040, but nevertheless robots are all prety much the same (except for some trills that you can programe). There's nothing like having other guy to play along. I now it's not always possible...
They prefer spending their time searching for the perfect new ball. When they find it, ittf's streaming will be much better. The players may look distorced but the ball will be always good for viewers :p
Now I'm playing with Xiom Hayabusa Zxi with Tenergy 05 on FH and Tenergy 25 on BH. I'm also training with Xiom Hayabuza Z+ (with a Tenergy05 and a Razka7, both boosted) and Xiom Strato (with tenery 05 and Xiom Omega Pro)