I would be very curious to know what is involved in brewing the kriek which they add and specifically if the beer is filtered once blended with the quadrupel. The addition of lambic yeasts into the mix could prove interesting when trying to maintain the overall character of the intended beer.
This beer is a solid quadrupel though perhaps not something you might like to start drinking if you haven't had many beers with a sour "edge" to them.
Cheers!