Hi,
The older Mk1 auto's did have some isssues, but the new Speedgear is very reliable. I have a friend who works at a Fiat dealer and he said they get very few problems, less than the manual version.
Maintenance is not really an issue, they need the fluid changed and filter changed, but not for a very long time (I forget when it is).
I think you can chip the engine, but the gears work at their most efficient so there is not much which can be done. There is a economy mode which changes up quicker, but I don't really use it.
Poggy