I've been discussing this turbo-gasoline-engines for about a year with most of my enthusiasts friends. I currently only have Chevy's V8, but are really interested in how this turbo-gasoline engine will evolve. Most european car brands are using turbos on their gas engines now (BMW, MB, VW, Audi, Porsche), and now Ford has it's own fleet of turbos.
We have the same questions: how long before turbos start giving trouble? how good it's the fuel economy? is it worth it?
I think the best answers have come from friends that have owned turbo-gasoline engines, like audis or vw, volvos, and all have had trouble with turbos. For some it's been easy fix, for some new turbos (pricey). I can talk for myself about owning a volvo 2000 s80 2.9 (non turbo), vrs a 2001 s80 T6 (double turbo). Prices on T6 have gone down the drain because of expensive repairs, and the regular 2.9 has kept it's price and it's a car I sold fairly easy. Yes, the T6 was a beast for it's time, but I got a hard hit with mainteinance and sold price.
I understand that turbos have gotten better over the last 4-5 years, and give that extra HP and torque to small engines, without compromising to much mpg. It sounds really nice. But on the long run I'm sure repair costs are going to be expensive.
It really depends on how long are you planning on keeping your vehicle. I would suggest that if you change your car every 4-5 years, or before 100K miles you will be doing fine with turbos. I think turbos will start giving problems (as mention above), around 100-125K miles, which, by the way, is a lot of miles. But I usually run most of my truck more than that before letting them go.
So, in conclusion, for some people turbo-gas engines will work perfect, and for some other people regular V8 will work perfect, as it has been with diesels or gasoline.I've seen diesel-turbo engines run for 250-300K miles without any trouble, but diesel engines are another story.
Please keep up the information about reliability, maintainance, and mpg, so we all can have a better opinion about turbos, and who knows, maybe in the future I'll have one.
Thanks.