There are no bad 944's. Only bad current/previous owners.
Being the owner of a 944, and having spent time speaking to, and reading/writing to, many 924/944 owners over the past 5 years, I can say that most 944 owners are dolts.
What did Tifo just say?! Yes, I said it. I am not trying to start a flame war here, so I need to qualify the above statement.
There are 3 distinct groups of 944 owners:
1. The DE/Autoxer/Enthusiast/Fanatic
2. The "I bought it because it was cheap and can't afford to, or are to stupid to, maintain it properly" owners
3. The concourse, factory-did-it-this-way-so-it-should-be-so owners.
There are a goodly amount of #1's, I'd say it's about 20% of owners. I am one of these. I drive the heck out my car at events on the weekends, but the car only sees about 3K miles per year. Everything mechanical is always kept up, and I modify/change things to suit my vision of what the car should be, but nothing from Autozone's Jessie James or TunerZ section makes it onto my car. My car is not concourse, but you can tell someone loves it. Usually there is always some part on my workbench waiting to be installed or swapped.
Due to the price of entry into 944 ownership, many #2's get into the picture, unfortunately. This leads to a downward spiral that just gets worse and worse. These owners never do the routine mainanance, let their car's paint go to hell, it looks like a family of bedioun sheephearders with a McDonalds nearby live in the car. I'd say that #2's represent about 75%. These owners really are the same owner that might have bought a 1990 Toyota Terdcell at a Buy-Here-Pay-Here, but saw an ad in the local Auto-Snaker for a Porch and thought "Hey, I can afford that!". The Terdcell probably would have looked just as bad in a few years as their Porch does on the interior and exterior, but the Terdcell probably would be able to put up with the mechanical neglect better than the Porch.
#3's are a rare breed. 5% of owners are #3's. These are the guys who are looking for the missing black interior bolt covers, or want to know the correct factory-supplied oil filter, or fret over the fact that they got a new stone chip. Their cars are cared for, loved, relgiously maintained (usually by a mechanic, not the owner). The car is often taken to concourse shows, but rarely driven in driving events, if at all.
911's would be in the same boat if the price of entry into the game was as cheap as the 944 price. But it is not, most of that has to do with the fact that the 911 is the car that people think of when the word "Porsche" is uttered. The 911 will always have a strong following and, let's face it, it is a great car and since it has been made for many, many years (40), it should be.
Anyway, that's my take. If someone buys a clean example, that has been loved, and they continue to upkeep and maintain the car as it should be, a 944 will last forever.