The Quadrifoglio is a pretty cool option to an M3 or C63. It's probably ok for a lease, but I wouldn't buy one or keep one long term. A high end detail shop had one of their 4C in for a clear bra a few mods. They said the quality and engineering compared to German cars just isn't there. Granted they were talking 4Cs relative to say Caymans/Boxsters and BMWs ...but I'd guess their sedans probably are the same relative to sedans from BMW, MB, Audi etc.
To be fair, the 4C is a special animal. Nothing but a Lotus Elise/Exige come close to offering the same combination of price, dynamics and driving experience--and neither of those are sold in the US anymore, nor have a carbon fiber chassis. The carbon chassis alone is so unique and exceptional at $60K, I don't think one can knock the 4C for many of its compromises versus the German competition, as it isn't really competition.
The Quadrifoglio is a totally different endeavor. It's meant to take on BMW, Mercedes, etc., head-on. Not saying that removes all doubt regarding Alfa's questionable history of reliability, but I certainly don't think you can extrapolate much from the 4C.