The 6.0 were problematic.. I had an 01 with almost zero issues.. I was considered lucky... The 6.4 were considered a step above the 6.0 but still had issues... I had an 05 with zero issues.. Except the PDF filter cleaning.... I also was considered fortunate... The 6.7 , yet again was plagued with issues,,, you will find many , many people not on this forum with zero issues , and you will find a few on this forum with a huge list of issues... Now I have the new 2015 6.7... Fingers crossed... With the proper maintenance schedule will be a towing beast all it's life , like it is now... The demand of these trucks are high... When I picked up my 15.. I got $31,000.00 trade on my 09 with 96,000 miles on it and 4 holes in the bed :B
Edited to include a proper date