These threads all seem to follow the same path which includes responses from owners, folks with other experience and the responses and critiques from those with little or no direct experience. The latter can be of some value, but with the appropriate perspective.
Then come the recommendations for something in a completely different category
So, actually having owned and still owning them (964, 996 and 986 S) and comparable cars for 20+ years, here are some thoughts based on my and several friends' ownership experience, which is up through the current models;
Positives
1) They are very reliable and relatively painless to own. Yes all cars have their weak spots (ignition switches, alarms, the IMS...), but on the whole our Porsches are some of the least painful cars to own, especially in light of their performance.
2) Porsche uses very high quality components, for the most part. Looking at the undersides of ours, the fasteners etc. have very little corrosion, hoses are almost perfect, etc. The interiors wear well, great quality leather, etc. The upside of this is when something does need repair/replacement and you use factory or OEM parts, it stays fixed...
3) They are very good for DIY maintenance, e.g. quality fasteners and the like make for easy removal and replacement of parts. Parts support is excellent. Oil changes, spark plugs and brake service for example, are straightforward with great access.
4) Great drivers...drive one.
Negatives
1) Things do fail and they do have some weak spots; do your research and because some issues can be $$$, get a PPI from someone qualified. PCA can help.
2) Parts prices are dear and some are very expensive, think Cessna expensive. Good news, is they don't break that often.
3) Access beyond basic maintenance is challenging, these are rear or mid engine cars. Aside from below, the Boxster engine is accessed through hatches. Price to pay for their capabilities.
4) They do best with OE or OEM parts in most cases. Brake rotors for an example, I have heard of several issues in our circle with vibrations from non OE/OEM rotors. There are other anecdotal examples. I have no idea why or how???
5) They can be expensive to maintain if anything major happens...I'd propose that one reason for their unfounded 'needy' reputation is from folks who buy a run out cheap one, expect parts and maintenance to be commensurate with their purchase price (not the ~$80K car it was), maintain it accordingly and complain about how bad Porsches are...
All years have their issues. Other less quantifiable factors also come to play; do you prefer the more analog experience of the earlier cars? The tech of the later ones? Earlier more traditional interiors? Flat screens or knobs? Hard to recommend what to look at or avoid. Me? I prefer traditional which is why I am looking seriously at a 930...
Do your home work and buy the best one you can.
Enjoy!