I haven't done one either, but been banging around with plenty who have. Take it for what you paid for it.
Shelby is probably the best, quite a bit more expensive, can go the biggest bore, and has a stronger head bolt design and double cross bolted mains (6 bolts per cap) and what the guys who are making the big numbers use
Pond is a favorite as well, and is cheaper, but is closer to a standard style block and a couple have delivered with sealing issues on the FE forum, all corrected by Pond
Genesis about the same, and Dove is a crap shoot. They quality control is horrible, and very few guys have anything good to say. When they were the only game in town, they were big, but now they seem to be a bit of an also-ran.
I'll be using a Shelby block when I redo the Mustang