Just bought 996 this week with little over 100k on it.
From my research, this model is pretty good overall. Its weakness however is engine. It can fail and at the moment no one in U.S. performes reliable rebuilding on it. Engine has problem with balance shaft bearings which can cause catastrophic failure. Also cylinder liners tend to be weak and can crack. Some of them leak oil out of rear main and/or balance shaft "cap". As for me that's not a big deal.
Good news is Porsche will sell you "new rebuilt" engine with upgrades.
Or you can have it reconditioned in England by company called Autofarm
this is a link to there website
http://www.autofarm.co.uk/ good read.
I'm planning to keep my 996 for a long time. It will probbly at one point need new engine but I knew that before I have purchased it. When time comes I will replace it with 3.6 or 3.8 liter.
So good luck with your buy.