By all accounts, macroblocking is at its worst when combined with a panasonic plasma. There have been tons of threads here and in the usa with unhappy panasonic owners and the Denon A11.
the panasonics own noise reduction circuits tend to exagerate the problem.
Now with the 3910 its macro blocking problem if seen is nowhere near as bad as the A11 was. infact when outputting in certain resolutions macroblocking just cannot be seen.
A demo unit i borrowed for home did display a very small amount of MB but as an owner of an A11 i can say many of the discs that were very bad on the A11 were MB free on the borrowed 3910.
Now i have a 3910 i am very pleased that i have not seen any MB at all and i have tried all the discs i know the A11 was bad at.( it should be noted that MB can be very display dependent as some users never noticed MB with the A11 either.well maybe there just not so picky

)
Thats the best advice i can give is maybe borrow a unit for home demo. but i think you will be fine, TBH