i've had my timberline for more than two years and i really like it. it makes a sharper chain the either a file or a grinder. i haven't used the grandburg but i have used the oregon version of the same filing jig and it can't come close the the timberline. i use an oregon 510 for friend's chains and a tractor supply clone for depth guages. i also use the 510 for repairing damaged chain, which isn't fun with the timberline, but for my fleet of 3/8" and low-pro equipped saws (don't ask me how many, i'm worse than imelda and her shoes) i use the timberline. i don't miss the lack of the legendary 10 deg. it doesn't seem to matter. not only are the cutters sharper but the edge lasts longer, maybe because they are much smoother or perhaps due to the the metal staying cool. it's also nice to have something better than a file to use in the field on the tailgate.
there are some downsides. when the top plate gets too short the burr hits the chain stop as noted in previous posts. and it's a good idea to lower the gullets with a file or grinder occasionally. the 5/32" burrs are delicate and easy to break while sharpening. take light cuts! don't ask me how i know. you can tell when you're done by the way the chips accumulate on the edge of the top plate.
over the more than two years i've had it i've worn out one 7/32" burr and broken one 5/32" burr. i usually sharpen my chains after a day's work. so they've had a lot of use. burrs will last a lot longer if you refrain from using them on a damaged or poorly sharpened chain, and, voice of experience, almost any chain that has been filed falls into that category. if you can, use a grinder to true things up, then use the timberline. otherwise just take multiple light cuts until things true up. one more thing, it works great on .404.
timberline's customer service earns a 10.