Hello BruceH, it's good to see a fellow Texan on the board. The only thing other than the IMS I would be concerned about is the very low possibility of a D Chunk failure. Problems that will hit though is the water pump breaking, Air oil seperator malfunctioning, CV joint boots cracking, and motor mounts disintegrating. These aren't flaws rather, but inevitable wear and tear. I'm not here to scare you, but be expected to have $2,000 set aside in repairs, as expected for any car with age, especially being a sports car. As for those problems, that is what I can think of on top of my head, but don't let it deter you. These cars have much character and fun.
Edit referencing D chunk failure:
"
This “D-chunk” problem seems to ironically occur mostly in gently driven cars. Boxsters that are driven hard at the track or on the street do not tend to see this type of damage. At least with respect to the track cars, one theory is that these cars tend to have their oil changed much more often. The problem affects mostly the 2.5 and Carrera 3.4 engines:"
Source:
http://www.pelicanparts.com/techarticles/Boxster_Tech/13-ENGINE-Common_Engine_Failures/13-ENGINE-Common_Engine_Failures.htm