I play with that grip, and it is very comfortable. My wrist never hurted at all, and if you think you can't generate pace with it you probably have never seen it in action. It is indeed difficult to read, and great for passing shots and hammering the other side of the court.
Defensively, you can hit "baseline lobs", balls with so much topspin that they are sometimes winners especially on a small court.
The downside to this grip is that playing volleys or forehand slices feels very unnatural, when you're used to hitting with the wrong side. Playing a good slicer is very tough (i mean for Mr everybody, not Bera).
And the grip is so far from a slice grip that when i have to do a defensive running forehand slice with little time, i have to hit it without changing grip but with the hand's palm facing backwards, looks weird but it works well and can do some surprising crosscourt defensive dropshots.
Berasategui's forehand was incredibly powerful, and he could hit impossible angles. He was immensly enjoyable to watch for a baseliner, his forehand could overpower anything and the backhand was very solid and looked weird as hell too, it went from two-handed to one-handed at the last instant, and with that wrong side grip. He wasn't a big server, but in 94 i think he won all his first week match points with an ace. Too bad his career at the highest level was so short
My all-time favourite shot is one of his jaw dropping forehand return crosscourt winners, when i say crosscourt i mean almost parrallel to the net from a just bit inside the court, a shot you would think was only possible in ping-pong, i probably slow-motionned that shot like 50 times at the time.
I also play the backhand with the same side, i couldn't believe it when i saw Alberto the first time that a pro would play with my self-teached freak grip.