I contacted them about refurbing mine maybe a year ago. The cost quoted was a fair bit below new (something like 50-65%) but I decided to go new due to the potential tangs issue. The labour cost on clutch replacement is going to be high, so even if they offer a warranty and fixed the part, it doesn't necessarily mean you'd save, plus hassle..
At the same time, I intend to get my worn clutch back and keep it in my garage for potential future refurbishment / just in case.
There is the tang, the labour, but the issues that seem to have been reported are in the set up. The problems *appear* to be that the friction properties of the material is not the same as the OEM spec so the adjustment / set up process goes out the window.
There have been several customers shouting about how they'd done it, and someone that is prepared to publicly say they are going to be a guinea pig. Without exception they've vanished with no evidence of the process being successful.
Martyn has a point, I would only fit a Maserati Original Clutch using an competent Indy or a Maserati Main Dealer, whilst they are in there get everything else done too. Yes it is expensive (around Â£2.5k+) but mine was last done before the centenary trip (2014) and i've still got 50% left and that includes usual the Centenary Trip, the Spanish Trip, one Le Mans trip, two Bruntingthorpes, and one trip to Llandow as well as general dicking about and commuting. A well installed and properly adjusted clutch should last years.