The Echo CS400 is advertised as a professional grade chainsaw. I don't know if that is actually true, because I am neither an arborist nor a logger. I also never plan to become either. With that out of the way, the CS400 is a much better saw than the one I was using before. I'm going to go into the things I like about the saw and the places where it could use some improvement.
Out of the gate the first thing I noticed was how easily it started. My old saw was a real bear to get going. It wasn't that it didn't start up after the number of pulls described in the instructions, it was that the recoil was very difficult to operate. I would sometimes have to pull it so hard that the saw ended up getting jerked away from where I was trying to start it. This absolutely is not the case with the Echo. I am able to start it very easily, using my weak hand no less. I'm pretty sure that most people could get one of these things fired up with very little effort. The saw also is built so that it has some flex to it (they call this the vibration reduction system). This seems to work, as I didn't end up with numb fingers like I did using my old saw.
Another thing I like about the Echo is the chain brake. The thing that I like about the Echo's is that if the brake ends up getting engaged (shit happens), it doesn't kill the saw. The chain doesn't move until the brake is reset, but you don't have to fuss with the saw to get it running again. Granted that this isn't such a bad thing with a saw that's really easy to start, but it's a nice touch.
The last thing I really like about this saw is where the chain tensioner is placed. On my old saw, it's on the front, parallel to the bar. On the Echo, it's on the side. This is a much more convenient location.
Now I'll get into what I don't like about the saw. The worst thing about it is the chain that it comes with. It's fine for cutting small branches and things like that, but if you're cutting larger stuff it just doesn't quite do the job. I replaced the factory chain with an Oregon S62, and it was like I have a different saw. I cut up a pine tree with a 14 inch thick trunk today, and the little saw didn't miss a beat.
Another thing that I noticed is that if used horizontally (like for felling and limbing) for a while, the throttle response slows way down. This does correct itself after a few minutes of cutting. My guess is that the float in the carburetor doesn't work right sideways.
My only other gripe about the thing is that it seems to run out of bar oil before it does fuel. This may simply be because I need to adjust the oil flow a little bit, but I cannot honestly say because I haven't tried yet.
At the end of the day my little Echo has managed to cut up about a cord of various softwoods with few problems. Changing the chain out made a tremendous difference. The real test will be how the thing works five years from now, but I hear good things from other people about that.