The point of developing the Mandolin 809 deck was suppose to be so USPC could/would print gaffs with altered back designs.
Has this happened ?

Definitely not. To make it worse Mandolin decks are the worst quality decks I’ve seen in a decade, even worse than Standards.

I have not seen any problems with Mandolin quality. Garrett Thomas uses them all the time (I would assume) since his "Speed Reader" decks are all printed on Mandolin backs as well as his "Stand Up Monte".

As far as gaffed backs, I think I have seen "Maiden Back" used more than "Mandolin" overall. Penguin seems "All-In" with Maidens as their marked cards are Maiden back and come pre-stacked in "Mnemonica" as their New Deck Order.

Before switching to Phoenix, I was exclusively using Mandolin (because of the Speedreader) and bought few bricks for duplicates, gaff making, etc. When my decks started running low, I didn't buy more and immediately switched to Phoenix. Still miss the m...s position of the speed-reader, but Phoenix are excellent and much better with my eyesight getting worse. Maidens are much better quality, but I discarded that option because the m...s are not always easy to read from a spread.

I still prefer Bicycle decks over all named on this thread

I will guess you mean either "Bicycle" "Standard" or "808 Rider Back" because every deck mentioned in this thread so far are in fact "Bicycle" brand (with the exception of Phoenix, even though they are printed and cut on the same machines in the "Bicycle" factory and go thru a stricter QC protocol than "Standards").