While I haven't enjoyed the use of a dedicated race car, I had a 911 that was 1) Bulletproof and 2) was well modified for track duty.
I sold my 911 because I wanted a "street" Porsche I could track on occasion. I did that this past weekend and one (among several) things came to mind.
A stock boxster needs a complete new suspension to be truly enjoyable on the track. It wasn't a bad car, but as I mentioned before, the lean, dive, squat etc under real track conditions was much worse than I anticipated.
Reliability. I have been a bit nervous since I bought the car about MAF, O2s, RMS's etc. As a street car i wouldn't worry about it. After day 1 at the track I enjoyed a Check Engine Light occurance which points to a camshaft problem.
Did I mention my 911 was bulletproof? Throttle it all day long, take a 4-6 hr trip home and never a hiccup. Same was true with my 914. The aircooled motors, with no computer controls, are simnplicity and reliability in one fell swoop.
You mentioned you dont like 911s and I can understand the aesthetic reasons. As you mentioned though, folks who really drive 911s well can drive ANY car well, they just choose to run a 911
All that mentioned, a friend of mine bought a Boxster S in 2001. Since folks wern't really "racing" them, he and the shop came up with some wicked, custom suspension stuff. And WOW was that car quick. Not sure I would say "fun" or "entertaining" but just fiercely quick and well composed. My guess is that it takes about $5k to make them handle in a manner you would appreciate.