My understanding was that the latches tended to fail after a couple years of regular use, but I’ve never gone looking for credible information to back that perception up.
With a little practice, the Peacemaker loads pretty quickly, but it is a cumbersome system.
For those who don’t know, the Peacemaker’s cylinder is accessed by a small port on the back of the revolver. You knock spent shells out one at a time by rotating the cylinder, then load fresh rounds in their place.
You can speed reloading, by directing the barrel up and rotating the cylinder with the port open, to drop all the spent shells at once. Then you direct the barrel down, and with your left hand you manipulate the cylinder while you use your right hand to feed the rounds in. (This might be one of the rare moments when shooting left handed is actually an advantage, as the port is to the left of the hammer.)
You’re not going to beat reload times for a semi-automatic, or even a revolver with a speed-loader (assuming you can get the speedloader to actually release the rounds).