We own and use several Echo saws. We didn't much care for the CS-440 and the CS-300/301's, but the CS-510's are getting a LOT of use, and holding up fine.
Although they aren't overly impressive anyplace, they start with 2-3 pulls, run FOREVER on a tank of fuel, and get the job done. We use them more than just "casually", they get the crap ran out of them all the time.
We just obtained the CS-360T, and right now the jury is out on that saw. It's supposed to be Echo's answer to the Husky 338XPT, and Stihl MS-200T, but I'm not overly impressed with it, and absolutely HATE the built in rev limiting module. They must think EVERYONE is so stupid they will lean a saw out and burn it up?
Anyhow, I rate the Echo's as among the best of the "low end" saws. We even run the larger 670, and have ran the 8100. By comparison, my Husky 268XPS is at LEAST 30 percent faster/more powerful. Every time I think an Echo is doing pretty well, I get out on of the Husqvarna's, so I can be reminded how professional saws are supposed to run!......Cliff