Been done, of course. Graffiti, while not perfect, is usable after only a short training period. But there are some potential advantages to the 8pen way. For instance; once I got used to entering 'the' I could enter the whole word with a single gesture only slightly more complicated than some letters. This is very fast, and while it certainly isn't true of every word the layout does place many of the common letters and combinations within easy reach. The payout of 8pen will come when the letters become second nature. At that point entire words can be entered in one continuos motion. Swype style keyboards can do this already and I think they are intrinsically faster, but they depend heavily on prediction. That means you always have to slow down and tap keys individually when entering unusual combinations, at least until they have been trained. These days when acronyms and l33t have all but taken over casual texting you could end up doing a lot of training.