I've had a pair of M&P Pros with the Apex Bar-sto match fit barrels since July. Due to being in 1911 mode until the IPSC Nationals, I've only had a chance to put a little over 100 rounds through one of my pair.
But they are quite accurate, groups average about 2" at 25 yards from prone. Apex was getting 1.5" groups with the new version ammo (I was using the reloads), and .73" groups with ASYM both off the bench.
Based on my experience, if you buy one of these barrels from Bar-sto match fit barrels, shoot the gun with the barrel fitted first before buying sights. Mine were 4" low from POA, so I had to do with a much lower front sight than what is normally recommended for the rear sight I am using.
Now I haven't talked about them at Apex's request, I didn't get the full story why until this afternoon. Apex still isn't offering the barrels themselves. Bar-sto is delivering barrels based on their own specs, and mine were custom machined from those barrels, to match Apex's specs. Apex is still continuing to find a way to deliver barrels to their specs. So my results may or may not reflect production Bar-sto barrels. I doubt that there is anything inherently wrong with the Bar-sto M&P barrels, nor did I get that impression from talking to Apex.