Generation after Generation....
I agree with everyone else. There is minor cosmetic differences between models, but performancewise, there is NO difference between the Generation 3 and the Sentria. The only reason I prefer the Generation 3 is that it uses regular screws, whereas G5 and later machines use Torx screws, so it's a little less user-serviceable. When I received my Sentria, the front nozzle was busted, so I used a nozzle casting from a Generation 3, and with a Generation 3 brushroll it works just fine, only difference is that the BPI is on the left side. As for the Diamond Edition with the two-speed switch, that's the only G series I don't have (I do have the conventional Ultimate G), but I understand the two-speed switch was discontinued because everyone was using it exclusively on high, and it burned out the commutator prematurely. Can anyone verify this?