I was having major arm problems and took someone's advice to try the Pro Kennex 5g and I bought it without even trying it out. The first time I used it, it felt like terrible - really flexible, no power. In fact the first time I used it I lost a match to a guy that I'd never lost to before and never since.
But after that poor intro, I grew to love it, and my arm recovered within a couple of months and that was a few years ago. I switched to the Bablolat Pure Control when I got a super deal on some, but only did so because they had same characteristics as the ProKennex. Headlight, heavy racquet, narrow beam. Arm is still fine.