I've had pretty good service out of my vito's. I had it down at Busco Beach this past September, rode the dog pee out of it, and had no trouble at all.
I know freek had that sleeve problem (which was a major issue) and all vito's 240 BBK's have terrible casting flaws from the factory but they're also known to run pretty stout when setup properly too. That 40cc's is after all a 20% increase in displacement over the stock cylinder.
If you already HAVE the vito's kit, Rock it! Just realize that you'll need more than just a bolt on BBK to be really putting out some power, you'll need to upgrade the carb, exhaust, airbox, and probably clutch.