I've had the Echo 770 for the past 4 years, and it is a beast. I bought it over the Stihl based on reviews and dealer recommendation (yes, he's got both Stihl and Echo...). The Echo is supposed to be more powerful, but really at that level it's a mute point. Like someone else said, it's the best yard tool I've ever bought; makes fast work of things!
Anyway, the Echo 770 has been great so far, really awesome power, and starts right up every time, one pull. I've got a mix of Stihl (chain saw, weed wacker and hedge trimmer) and Echo (chain saw, blower and hedge trimmer) power equipment, and both brands have been good. My Stihl chainsaw does start much harder (more finicky to start) than my Echo chainsaw, and the Stihl weed wacker has an annoying throttle/power lag, but is otherwise a very nice piece of equipment. I always like the idea of getting Stihl equipment, but honestly, in my experience, the Echos have been simpler/easier to run. But again, I like both brands.