I have a 2004 S. Flirted with (test drove, configured what I wanted with my salesman) upgrading to 987S in 2007 when the 3.4 came out. Then again with the RS60 in 2009. But it was 2011's Spyder that really gave me a serious jones. Test drove a used one with a handful of miles that summer, tested a showroom floor one that someone ordered then changed his color preference when it came in so it was on the floor awhile.
Finally came down to the reality that, with a 50k price delta (when tax was figured in), I just didn't want to do it. As you said, Rondo, each time the difference just wasn't enough to warrant the price differential. I only have 43k on my S, it's in perfect condition, and I just have no real desire to upgrade when my trade-in value would be so low and the next guy would be getting such a screaming deal on my current car!
So I just put new wheels and exhaust system on my car and bought myself a bit more time. Of course, as soon as I did I started looking at used Spyder prices and realized I may have been a bit hasty!