My wife has black Spider LE, it is completely faultless after 15 months and just fantastic to see sitting on the drive. Everyone is impressed by it.
Reliability on modern Alfas is really no different from any other premium brand, as someone set out above the components are all very similar in all marques these days!
All you need is a good dealer and you have at least one nearby, Mangoletsi of Knutsford, Cheshire. Piccadilly are supposed to be good too, they're in Knaresborough I think.
Go for it!