I've got one and really like it.
It takes a little getting used to but once you get the feel, it's easy to use and yields great results.
It's important to take small bites when sharpening. You might have to make a couple of passes on a very dull chain and four or more on a chain that's been rocked. Taking small bites extends the life of the cutters as well.
I got a chain vise, from forum member Homelite 410, it works great with the Timberline.
I sharpened a chain for a neighbor who has always sharpened with a file. He was so impressed with the results that he bought a Timberline and is planning on ordering a chain vise.
The key is to take your time initially and get the feel of using the sharpener.