Heh, its quite more than "supposed". Its quite real infact. I myself have never had the 2.7 sludge problem, but that's because I bought my trep with a blown 2.7, from the sludge problem. I have since converted it to a 3.2, along with about 60 other Intrepids and Concordes, with different "sludge induced" or other 2.7 problems. Heres some 2.7 sludge pics FYE:
I have never been a "sludge victim" myself, but many have. Failed oil pumps, timing chains, water pumps, and chain guides are a common result of sludge. Sometimes, just the waterpump failure causes it.
On the other hand, there are many people, and members here, that have nurtured their 2.7 properly and have made it last well beyond 100,000 miles. Thats an accomplishment if you ask me. The average failure rate of the 60 or so cars I converted was about 65,000 miles, all 2.7's, either sludge or water pump related.