2011 Kawasaki KX250F Review - First Impressions

I've been reading on a few websites (dirt only) that while the 250 four stroke might be fast and all that, it weighs more than its two-stroke counterpart, and has to run in the former 125cc class. Is that true? Also, I hear horror stories of two fifty four strokes blowing up, and needing to have the whole motor replaced. I'm in the market for a nice 250 for my son, and was wondering if this would make a good 2nd bike, as he has about three years on a ancient 100cc XL185 Honda. Thanks guys.