I like the quote at the end of the article.
I know it has probably been posted before but it's good to read again.
I can't be bothered going back thru all the posts.
http://www.motocrossactionmag.com/Main/News/TWOSTROKE-VERSUS-FOURSTROKE-MOTOCROSS-SHOOTOUT-YAM-7117.aspx
The 250 two-stroke is a superior machine in most ways, but that superiority has to be perceived and acted on in a crowd full of valve-and-cam sheep. 
Actually, the last 3 paragraphs is worth posting to sum up why it hasn't caught on faster yet:
"The MXA wrecking crew doesn't want you to run out and buy a bike just because we think it is the winner. We want you to look at the strengths and weaknesses of the YZ250 and YZ250F (or any two-versus-four match-up) and add that to your personal strengths and weaknesses.
Logic says that since lap times are virtually identical for the same rider on both bikes, that the real difference comes down to the battle of ten horsepower over an easier-to-ride chassis. For a racer, starting on a typical dirt starting line, the YZ250 two-stroke should always get the holeshot. If the 250cc two-stroke doesn’t beat a 250cc four-stroke to the first turn, the rider should retire and take up mushroom farming. The YZ250F four-stroke should never be able to overcome the ten horsepower disadvantage in the first 200 feet. From that point on, it's a matter of whether the track has the kind of conditions that will force the two-stroke rider into making a mistake. If he doesn’t, he will keep the lead to the checkered flag.
Does that means that the starting gates are going to fill up with YZ250 two-stroke riders? No. The average 250 Novice or Intermediate has no 250cc two-stroke experience and it will cost him the price of a YZ250 two-stroke to gain that know-how. For most riders, with average talent, the difference won’t be worth the extra cost. The 250 two-stroke is a superior machine in most ways, but that superiority has to be perceived and acted on in a crowd full of valve-and-cam sheep.
