I'm a guitar teacher and have been using this with my students. It isn't perfect, but it works. It is a little quirky in the way it enters notes.
Biggest downside is that it is hard to get it to show all the music clearly on one screen.
Otherwise, it is great. It has full tab capacity, with a guitar-neck visualization and input ability. It has a grid-style drum editor, a mixer, playback speed adjustment... It can do all varieties of tuplets and time signatures and alternate guitar tunings. I even got it set-up to do two 5 string tab-staffs tuned to each side of a Chapman Stick.
It can open Tabledit, Guitar Pro, and Power Tab files. It can export to Lilypond format.
What more can you ask for FREE?? All the other tab programs out there have quirks and issues too. The best for professional use is probably Finale or Sibelius, but you have to buy the full $600 versions if you want true flexibility in tab and in time-signatures for those programs. Otherwise, Harmony Assistant is good, and Guitar Pro or TablEdit are functional. But Tux Guitar is good, and free. For me that means I can get all my students using it without hesitation, despite its quirks.