It's 5 speed, yes. It's generally reliable (The petrol models have a ZF 5 Speed box which is commonly found in most Audi's as well, the diesels have a GM unit) but there are reports of failiures around 80-140k miles. Half the internet things this is because the 'Sealed for life' gearbox oil is nothing of the sort and should be changed. The other half thinks it isn't - so really, be aware of the potential. Some of the 5 speed ZF boxes can lose reverse. Can't remember why.
I went for a manual because it was less reliability hassle (And then I got an entire new transmission fitted anyway, lol), slightly more economical (Not a major factor in the decision) but mostly because... I like manuals and enjoy driving them more. The Sport model is great in that despite the cars size its still good fun to chuck around a nice A road (It's a bit big to properly cane down a narrow B road).