Bad. This way of playing was labeled "mimic the dealer" in the famous paper "The Optimum Strategy in Blackjack," written by Baldwin, Cantey, Maisel, and McDermott and published in the Journal of the American Statistical Association in 1956, in which the authors calculated a -5.6% expectation (house advantage) against a player using this strategy. In Beat the Dealer, Ed Thorp later revised the number to -5.73%.
While this mode of play sounds reasonable, what makes it bad is that you lose on the "double bust" -- the occasions when the player and dealer would have both gone over 21 if the hand were played to conclusion, but isn't because the player acts (and busts) first. This effect alone gives the house an advantage of about 8%. Adding back the approximate 2.3% you gain for the 3-2 bonus on naturals gets you to -5.7%.
You make up the rest by playing the correct basic strategy, with the gains coming from (in order) proper hitting/standing, doubling, splitting, and hitting soft 17 and 18. These are options that the dealer doesn't have, and, that used correctly, accrue to the advantage of the player. Hence, eliminating them from your arsenal is detrimental to your result. As you can see, learning the proper basic strategy for blackjack is a must if you want to enjoy the low house advantage that the game is famous for.
