Helen, the manual gearbox is an absolute peach on a Porsche. Infact the best manual gearbox I have ever driven. A word of warning though the gearshift is really stiff in the first 1,500 miles of driving on a new car and takes are fair bit of arm work to get in gear. The same can be said of the first few miles on a winters day from a cold start. Don't let this put you off as once the car is up to temperature it slots beautifully through the gate. There is a short shift option but I personally would not go for a short shift gearstick as aparently they are stiff most of the time. The gears have a far more 'mechanical' feel than say a BMW. The clutch is not overheavy either so no problems there.
I would say auto option is more for a 997 if you are using it as a long distance cruiser.
Enjoy your test drives and let us know how you get on. You have got me tempted as well.
On the depreciation front honestly the more you spend the more you loose. You only have to look at sites like Rennteam to see people who have put 10k of options on a boxster/cayman and they are worth the same 2nd hand as cars with 3k of the right options.
And anyway if you start to replicate BMW spec's i.e. auto dimming mirrors, auto wipe etc you will spend £2k on stuff that imo you won't give a monkeys about once you have the car.