Pmag 40s are just as reliable as the 30s. I still some some of the old Sterling AR180/15 40 rds, these were the cat's meow back in the early 90s and man did I pay for them back then!
I have a few of the Bulgarian made 40s for the AR platform (before Magpul came out with the P40), they also worked just like any other AK mags, metal lined feed lips and robust.
Bulgy IK520 mags
Beta C-Mags ruled the AR15 Drum kingdom, but no one uses them anymore just because 90 rds onboard is quite a load. Best way to load CMag is a modified Lula (removal tab cut off to fit in between tower and right side drum) and judicious application of powder graphite every 5-10 rds. Yes, a PITA I know, but it is the only way I know of to ensure 100% reliable feeding under the clock.
Don't know anything about the Pmag D60s but they look cool.
SF 60 Gen 1 was a failure in my book, sold mine after a few range trips. I heard Gen 2 is better but no experience for me.