I like my Selespeed Abarth. Driving home on quiet roads, it's like a computer game changing gears with the paddles. You don't have to take your hands off the wheel, and it's so easy to get the right gear for the corners as it's quicker and easier to change with the paddles.
It's a right bugger getting back into a manual though! I had to move a friends car for her and I'd completely forgotten how to use a clutch.
The semi-auto box does make for more complexity on the car, so one more thing to go wrong. When I bought my car the gearbox was leaking oil onto the clutch plates, which took about three visits to the local Fiat garage to fix. Luckily, the dealer paid for all this as the bill was well over a grand.
Overall, I'd choose the semi-auto box over the manual every time.