scully and the rest of this newsgroup seem to have forgotten something. in seeing the episode where barney takes helicopter lessons again in syndication, i noticed that at the end barney does not stay sober. it seems he's addicted to coffee. but the "camera" flashes to moe who served him the coffee... "Nobody gets away from Moe" and he disappears in the smoke. Barney chugs down a six-pack of "coffee" and is back to his old drunken self again, complete with the appropriate barney beer belch. it didn't even seem ambiguous that he was an alcoholic again.
in response to those who think that moe hooked him with coffee, it would be completely out of character for moe to serve him coffee and not some alcoholic concoction. also, everything always ends up as it began, so the "continuity" of sober barney has no context.