I have pretty much given up trying to actually hit balls from my ball machine using the pseudo-SweetSpotter I built but I've found it is a great tool for warming up before a match. I'd compare it to swinging a weighted baseball bat while in the on-deck circle.
It really helps me focus on getting my swing speed up and since it has a tennis racquet handle it feels more realistic to hold. I've been keeping it in my bag and swinging it before matches and it seems to help.
A Head Microgel Radical, a Neos 1k, and a Silent Partner Star. Life is good.