We had no major problems with our Sele at all, over four years of low mileage ownership. I do feel that to develope real enthusiasm for electro/ hydraulic/ mechanical boxes, you perhaps need the more costly versions?
If it makes you feel better, having been involved in the periphery of these systems, they are actually all almost identical.
They all sit on standard manual transmissions, most (the Aston Vanquish Ecepted) with a lower first gear ration to help the clutch (why astons eat them!)
Your humble Marelli Selespeed unit as found on your Alfa and Fiat, is a descendent of the first formula one system, and is virtually the same as the units found on the Ferrari's Lamborghini's, Aston Vanquish and even the new Lexus LFA.
The BMW SMG system, although built by VDO Siemens, is made under license from Magneti Marelli.
With the development of what was originally Porsche's Le Mans PDK unit first into the VAG DSG, and now filtering in through Ferrari, Mitsibushi, and even Porsche, the Selespeed is no longer being developed much further for road use.
If it has really caught on, it wouldnt be a problem, as more people would have been trained, and teh experience diffuused down, because - its actually pretty simple, but it is a precision device that doesnt reward meddling.
The black mark for Alfa and Fiat is the poor stressing of the top of the gearbox, which can crack and leave the actuator without a fixed datum, which aint the Selespeeds fault.
If you really, really want one, buy agood one and search out an expert who can assist when issues arise.
If youre about to buy one just because its cheaper than a manual - I would leave it alone.