Having read all of the above with interest, I guess the main reason that I have reservations about teaching only tab (as opposed to dots, chords etc) is that the guitar is the only instrument to which tab is applicable. Dots, however, are used by every other instrument under the sun and a knowledge of how they work makes communication with musicians who are not guitarists much quicker and easier. However, as I said above, and several of you have also opined, the more skills you have on the guitar, the better a guitarist you'll be!