I will agree that it can be a double-edged sword. Like anything medicinal, it can turn into a poison if used incorrectly. Ultimately, though, what this world c

I will agree that it can be a double-edged sword. Like anything medicinal, it can turn into a poison if used incorrectly. Ultimately, though, what this world championship proves is that we need to get rid of the distinction between "classical" and "blitz". The "classical" world championship was just decided by a few games of rapid. Fundamentally, the question is how to get good at "chess" - thinking fast and slow. Over-training at any one time control will weaken you in the others. But will increase your overall strength. Some players (myself included, 2400 bullet and 2250 classical) probably need to spend more time training and playing classical than bullet. The vast majority of players I encounter are much weaker in blitz than in classical, including many IMs and GMs. For these people I would prescribe a few thousand games of bullet chess, fix 'em up right quick.