I have had some examples of Pilsner Urquell that SCREAMED diacetyl. Some cans and draft versions were very noticeable. Some bottles were better. When I drank it in and around Prague it was much, much cleaner.
While in Prague, and Plzen (visiting the brewery), we never noticed any diacetyl. When in Frankfurt, I always went for Czech beer vs German beer.
The only off flavor noted in bottles here is an old, cardboard taste. Simply from not being a fresh beer. This trait is shared with many imports, unless you can snag a 6 pack that is only 3 months past it's packaging date.