i have one....they do have their uses, wouldnt use one in an everyday situation, it is after all just a rescue ascender. extremely simple and very safe though! i wouldnt want to use it on arb rope due to the ammount of picking it does at your rope....its fine on kernmantle though.
oh, with regards to the picking, i bought this up with the guy at my local rock climbing shop, he was of the opinion that although it does pick the rope this actually does less harm to a rope then would a cam device that physically crushes the core. interesting
If you decide to get a Tib be sure to read the instructions and get the proper biner to use. To work properly it takes one with a proper dimension and profile.
When they first came out I bought one and used the right biner. The rope I used was a 7/16" KMIII static line. After a couple of days there were so many pics it looked like a herd of cats used it for clawing. Not my favorite piece of kit.
The Tib is not a popular ascender on the rockclimbing forums where I lurk either.