If you're perfectly happy with how the car is stock, then cool, I completely understand the hesitation. For some of us, we want something more. Sometime more than what the manufacturer decided they had to do to comply with EPA regs & CAFE fuel standards. There's never a sure-fire method for finding a good tuner - everybody has SOMEBODY thats been upset. But factory stock DME's or engines et al fail on the rare occasion as well. For me, it's a trivial issue. Do my research & due diligence, find somebody who's been in the business a long time with a prove track record, and start asking them questions. If they respond with logical answers that make sense, then ya - to me, it's worth that risk. If I feel they're blowing smoke or won't tell me anything at all - I'll pass along to the next.

In short - it all depends on what you want out of the car, and your assessment of risk. if you're modding the car at all - a good ECU tune is pretty low on the list as far as risk to the long term life of the car goes.