V8 and the engineering challenge

[Kirk]

Well it looks as if the (re)introduction of the V8 to F1 is happening. Theoretically, less cylinders equals less moving parts hence more reliability and cheaper to manufacturer. Which brings to mind many questions, mostly from an engineering perspective. Just what are the challenges involved? Can teams like Sauber, Red Bull, Minardi, Jordan look for a less expensive solution to engine supply, for the simple reason that the engines are less state-of-the-art? Or, is the opposite true, squeezing more horses from a simpler configuration and maintain reliability (for 2 races yet) is a gigantic challenge; so relying on the BMWs and Ferraris of the world to get it right would be a prudent decision? Thoughts?