OK, I know this is a "tools that are good thread", but...
I have the chain saw sharpener but have not yet used it, bought it this past fall but still use the files on an *** needed basis. I have 3 or 4 chains that need the sharpener though just waiting for some free time...
If you can find your receipt and you haven't opened it yet, you can still take it back. Their sharpener is a knockoff of the Northern Tool cheap sharpener, which is a knockoff of the Northern Tool $100 sharpener, which is a knockoff of the Oregon 511A sharpener.
I went through four of those cheap pieces of crud before I gave up. Too much plastic, too much vibration, too much wiggle equals no accuracy.
I just received the Northern Tool knockoff of the 511A. The fit and finish is not superb, but it only takes a few minutes to tune it up with a little sandpaper where the movement is rough. It is night and day difference from the HF tool, though, and works very well. One feature it has that the cheaper ones don't is the ability to tilt the chain 10 degrees (required for numerous chains). This is their $119 version, although it was just on sale for $85 in December. (oops).
Timewise, once everything is set up, I can sharpen a chain faster than by hand. However, sharpening by hand is still a little faster because you don't have to take the chain off the saw. The grinder takes off more meat from the tooth, but it is more accurate. My thoughts are that I'll use the grinder every 3rd sharpening or so, and file by hand (or with my Dremel tool attachment) in between.