Ever since Mario Kart Wii, Nintendo has changed how the power sliding mechanic works, and for the better I might add. The left-right waggle method was a hold over from the Nintendo 64 days when an analog stick was shown as a worthy method for contolling games, but as time went on, it became more and more apparent for snaking to exist within the franchise since then. Yes. This includes Mario Kart 64, Double Dash and the DS iteration. So when people cry afowl about the new drift mechanic introduced in the Wii version, there's one important factor to keep in mind.
Both Mario Kart Wii and Mario Kart 7 rely on the player to hold onto the drift button to execute two levels of boost. However, you can obtain a boost faster should you take the turn sharper. If you find a sharp 180 degree hairpin, come at the turn from a wide angle, turn sharply against the curve and you'll find yourself with a level 2 boost in no time. It's actually a very nice mechanic that also works for people who are just coming into Mario Kart, since outside of instruction manuals, it's not really explained. So for those who are jumping in for the first time, it's a much easier tactic to understand.
Now, if you look at Sonic and Sega All Stars Racing, they did the whole "Hold the drift button as long as you can to charge your boost" which is the most broken and horrible way to use the mechanic. How quickly you gain a boost depends on the weight class of the character selected. On top of that, the producer, Steve Lycett has gone on to explain that the drift boost mechanic was made so that all characters can obtain the same top speed if they charge their boost all the way up. But because some weight classes have a harder time taking corners, plus other techniques such as holding the D-Pad and analog stick in the same direction can change a character's direction and if carefully done can hold on their boost, it's completely breaks the game and renders several drivers effectively useless if you're looking for a fair race for first place. Item's won't help you as homing rockets will either be cancelled out by the lead's weapons, or they'll just destroy themselves if the lead racer is too far ahead.
So fret not race fans, Mario Kart's got your back.