As a tiptronic user (and casual manual user) my perspective is different.
I chose a tip, because I do a lot of traffic driving on steep hills, a manual would have killed my knee by now.
The Boxster gearbox has 5 mappings. If the car senses you're driving aggressivley, it will choose the aggressive mapping for you on the autobox and will change up much later and change down later. Vice versa.
Most people that drive manuals and try tips always seem to leave it in auto most of the time and subsequently think (rightly) that it is a boring experience. When leaving the box in auto (as in most autos) there is a big delay when you put your foot down, to it changing down and finally giving you power. This, I find, can be dangerous.
Personally, I never leave it in auto mode, as I like to be in control. In manual mode I think it is a very nice experience, and not jerky like the SMG in BMW's (although that doesn't use a torque converter and is strictly speaking a manual).
In manual mode you can keep your hands on the steering wheel and get gear change speeds on a par with manual gearbox changes (for many of us mere mortals anyway), you will never stall (the box will automatically shift down for you - but never obtrusively) and you will never kill the engine.Most importantly for me, the manual mode lets you keep the revs high without changing up for you, so you can stay in the high torque range, and can assist you with engine breaking. You will never have the expense of buying a new clutch either!
I eagerly await DSG though, as it's supposed to be light years ahead.