I have very mixed feelings about magic rack. After using it from time to time, I gotta say, I think the pros outweigh the cons. I really do love racking up the balls in under 5 seconds KNOWING there is almost nothing I can do to rig the rack. I've had nights when racking the balls took minutes. It would totally kill the momentum. As the breaker, I hated waiting. As the racker, it kills my back and annoys the hell out of me. Magic rack just solves it.
The only con to magic rack is that it's arguably too easy to pocket balls on the break. I honestly don't know what the actual statistics are but I'd be interested to see. I'm sure out of 100 breaks, the magic rack will probably add an additional 5-10 breaks with pocketed balls but it will also eliminate nearly all slugs (also between 5 and 10). Personally, I think this isn't a bad trade.
Does it give the better player an advantage? Probably. But, then again, the better player already had an advantage by being better, right?