i hate to be "that guy" but i will chime in by saying that dysons [period] are medeocre at best.
the statement that "dysons never loose suction -even a tiddly bit-" is a flat out lie. i just serviced a DC17 with no suction. i thought "clogged hose" checked that out nothing. then i thought "the fill tube" nope, the cyclone itself is so packed there is no suction, you pull it off and put on a new cyclone and the power is back.
anyone who has serviced a dyson's cyclone will find that there is a immense amount of fine dust buildup, recent machines make it so you must remove the permenent silicone gasket to access the cones, the whole process is a nasty dusty hour of work.
it is true that dysons dont loose suction when new and clean, put some miles and buildup on it and it will suffer. ALSO the huge reason why it looks like you picked up so much gunk and doesnt loose suction even when full is because it keeps the dirt loose and fluffy, ANNNND the volme you can take up in the bin is teeny tiny because it holds that huge cyclone, so even full there isnt much gunk in there to restrict flow.
they ARE easy to use however they are very very difficult to repair.
they are fun, cool looking machines with neat commercials, however the machine as a whole is no better than the eureka boss it sits next to at wal-mart. (i actually think the eureka is better)
in the end there are MUCH better machines out there for much less money, but! who else makes a million different models in a million different colors with a million different commercials?? no one, THAT is the key to dyson's success and appeal.
me im all about flat out proformance