I have responded to many threads of this nature over the years and try to give prospective buyers a fair picture, although for some it may turn them off. I am on my 3rd M96 car after decades of Porsche ownership and I must say they have just kept getting better, even though all Porsches throughout the history of the company have had their individual issues in all product lines. Some are worse than others, but all are expensive to fix. That being said, normal maintenance and regular driving are the best insurance against catastrophic failures in all things Porsche.
The 15k mile oil change interval Porsche recommends is IMO a dangerous practice. I sold my first Boxster a 97 with 120k+ miles with no engine issues ever, no oil leaks, and only the known trouble items, ignition switch, water pump, auto climate control unit, radiator overfill tank, MAF, in addition to normal wear items. Overall it was a great car though a bit underpowered for my tastes which is why I sold it. During the same time and after I had a 2000 996 Tip which I used as a daily driver for 2 to 3 years, selling it around 70k miles. I had 2 bad water pumps, ignition switch, idler pulley plus wear items and that was it. I changed the oil every 5k miles on both. No oil leaks, no engine issues and one of the most reliable cars I have ever owned.
My current car a 2001 Boxster S I bought with 40k miles and have had zero issues with the car thus far at 55k miles. However, for performance reasons and for long term piece of mind I opted to invest in the full performance upgrade to a 3.6 liter from flat6 innovations. I am getting significantly more HP than stock, more pertinent I have added torque and throttle response associated with additional displacement and a light weight single mass flywheel which makes a huge difference in the feel of the car. It is quicker by a long shot than my 996 and easier to drive fast if not actually faster than my E46 M3 which is a little better than stock itself having after market cold air intake and cat back exhaust.
The extra performance is great, but getting upgraded cylinders, conn rods, pistons, IMS, valves, etc, and perhaps most advantageous to me; the expertise of Jake Raby, flat6, and L&N Engineering having done the development and ongoing maintenance to my motor, assuming it ever needs anything. I say this because prior to this development we were at the mercy of Porsche's engine exchange program and they were not overly concerned about those who bought their Porsches on the used market. Jake and Charles have changed the landscape of ownership of M96 cars and right now is the perfect time to buy. I now have what I believe is the car Porsche should have provided with an 01 Boxster. The car is lighter, the performance better than the new 987s and perhaps just as reliable as the new engines Porsche is building without an IMS. I still have way less in my car than if I had bought a new 987 and I intend to keep it as long as it runs, which at my age may be longer than my engine
We have yet to see what issues the 9A1 will introduce, but hopefully Porsche has worked out the kinks in their water cooled engines. We'll know for sure when they start using it for GT3s and Turbos.
The bottom line is the Boxster handles better in stock guise than all but the most advanced 911s, and hence most road cars available, has two boots that provide ample room for luggage for two on a trip, and can be tracked successfully, if that's your thing, regularly, in spite of being a rag top. Amazingly the price of entry for a good car is ~15k or so. As with all Porsches and most used cars you should get a $300-400 PPI by a qualified independent mechanic who works on these cars regularly. I wouldn't use a dealer since they mostly replace parts under warranty. Once purchased I would advise at a minimum the IMS upgrade from flat6 and at the same time a new clutch, so figure those costs into your price of admission, then enjoy.