An electronics engineer (an authorised service engineer for the likes of Yamaha and Ampeg) explained to me the difference between digital, solid state and valve...and it made complete sense why people say class D is good but just lacks something. Suffice to say I won't be buying one in a hurry.
He also explained why they can be unreliable.
Just to add, I'm probably one of the weediest, skinniest blokes on earth and I've also got a bad back due to work. However, I don't have any problems moving my Ampeg cab around, it weighs over 35kg. COME ON YOU LOT, MAN UP!!!!!