I think that's one of the great things about the Rebellion. They pretty much picked up whatever tech the Empire didn't use (or stole what the Empire planned on using), and used it against them.
Guess the Empire should have kept tabs on their stuff.
Well compared to what the Empire had at the time, the Clone tech isn't all that great.
I mean it certainly gives the RA some better support, but it isn't like they would have large amounts of the tech. Though they did get their hands on a factory and got ahold of some AT-APs and even some AT-XTs(which i'll cover them some other time.)