Strictly speaking, the Fiat is not an automatic gearbox. Fiat describe the Comfort-matic as "an innovative robotised transmission that combines the advantages of a manual gearbox (simplicity, fuel efficiency and performance) with the practicality and comfort of an automatic transmission."
It's been around for some time now and I'm not seeing the motorhome forums flooded with reliability problems. There are some known issues exacerbated by people not reading the manual first. I'm done over 22,000 miles in 3 years with a 130bhp plus Comfort-matic. Total reliability but not necessarily perfect.
It's slow off the mark in 1st gear so fast roundabouts need to be taken with care [its no slower than a lorry]. It can get confused by rapidly changing terrain that requires frequent gear changes - it can't keep up. It does have a sequential manual mode so when it does cause me some problems - usually on the seriously undulating hills of the Pennines, I switch to manual just with a sideways flick of the gear lever.
I find it provides effortless motoring in the UK for over 95% of the time. It's particularly useful in heavy traffic or when needing to make tight manoeuvres because it provides smooth operation.
I'd recommend the Comfort-matic. I'm just not totally convinced that the premium price is worthwhile. I'd probably prefer to spend the money on a 150bhp engine. However, if you want easy of driving, or have trouble changing gears manually, it will probably be some of the best money you can spend. If you can afford it and already have the 150bhp or bigger, then motoring nirvana is just a little step nearer.