I ran a Boxster S for four years and traded it in for a 911 C2 which I again ran for four years. Both were manuals, and running them back to back was interesting. I loved the Boxster S, it was agile, quick enough, had great brakes, an excellent roof system, and reasonable practicality (i.e. adequate luggage space for a weeks holiday in France).
There was an element of the Clarkson pressure (you know, the "...you only buy a Boxster if you can't afford a 911...") behind the 911 purchase. In some ways I felt that the Boxster S was the better all round sports car, but the 911 was a more rewarding drive if you drove it well... it didn't take kindly to clumsy or lazy inputs though! The best option on the 911 was the switchable sports exhaust... lovely noise on bypass
Should have said... I bought a very late model 996 Carrera 2 (in 2004) with the 3.6lt. 320bhp water cooled engine. At the time, I had the option of trading in the Boxster S against a lovely one owner late model 993 C4S for slightly less money, but the 993 felt old, noisy and ergonomically un cohesive compared to my Boxster S. By comparison, the 996 911 shared much of the panelling and interior with the Boxster and I just felt more at home in it. Servicing on the 993 was considerably more expensive too.
Being new, mine only had routine main dealer servicing, at about £300 to £350 p.a. I had no other expenditure as I sold it after 4 years with ~11k dry miles on it - the next owner got a lovely car. I feel that the later 3.6lt. engines were better sorted, especially the cylinder liner issues. Regarding residuals, I got just over 60% of the purchase price back in the part ex, which is better than most run of the mill machinery, so overall it wasn't a bad all round ownership proposition.
With 20:20 hindsight I'd have been better waiting a couple of months and going for the much improved 997, but my logic at the time was that I'd rather take a well sorted end of run 996 than order a new untried and tested 997 unseen... Wrong
So, PaulJ, I'd go for a late 3.6lt. 996 or if the budget permits a 997, Carrera 2 manual of course
The slow depreciation is not what it was. The "normal" 996 and 997s tumble pretty quickly these days. This does however mean that picking up the next one becomes a reality (although I keep putting it off). Real world example - mine was £19K in April 2010 with 60K on the clock. Today it would still be in 5 figures but only just - and that is because it is a good one - no crunches, no engine problems (not for sale). I don't really consider £9K depreciation over 4.5 years for the miles that I've covered to be at all bad, but it is all relative and the next one probably base to be younger than 2008, under 40K miles to make it worth swapping - and that is three times the price that I can get for mine. I will change one day, I suspect that mine hasn't got much further to fall if looked after (although I have heard of people with Boxters picking up a second one for spares - they are so low in value).
The important thing is that 911s today are more accessible than they have ever been. The old adage of being able to afford to run one still holds true though - if you are unlucky they can be very expensive. It's OK when the "non Porsche" part fails - but when it is a "Porsche" part then be prepare to dig deep. The water pump is a good example. It is a Porsche pump and buying an aftermarket one is a known mistake - so that water pump is going to cost you £600. This doesn't of course apply to those looking at air cooled ones - but neither does "more accessible than ever" - good ones are very expensive - poor ones are on the way to being even more expensive!
The 911 is the only car that I've owned that puts the smile on my face like the Mog does - there is just something about that pendulum swinging about behind you that is even there with the 991. A lot less scary than it used to be, but then again they're a lot faster too.
Thanks for the advice and stories of ownership everyone, very useful with a car I know little about. It's an itch I ought to scratch one day, but before then, I've been getting strangely interested in a 4 wheeled Morgan, but who knows?
Appreciation or depreciation is just a factor of availability and desirability. The water cooled models have been made in vastly larger numbers than their air cooled brethren. However the water cooler but limited models (gt3 gt2 etc) have all held or appreciated over time and will be collectible.
I love my 76 lux with an updated 3.0sc engine. It's light, narrow challenging to drive and consequently fun. On the downside I may be reaching the end of my tenure with it as it just won't fit 2 small children and me in it. Despite what I told my wife when I bought it....
It seems that you are in the wrong place to be talked down from the place you are standing on, but, don't worry help is at hand. Surely the piping around the seats should have been in blue, not red? There, go off, have a drink, and think what a lucky escape you've had.
You know it makes sense! 
