Hi John!
I have an old Big Power BP08 which I'm quite satisfied whit, the suction is just awesome, and the power nozzle does a really good job. Like Karl said, I don't use it so much, just when I have the time because it's a mess cleaning the tank and all the baffles that are inside to separate the air from the water after each use, but there's a new model that uses a separator like the Rainbow so it'd be more easy to clean I think.
Mine is terribly loud and very heavy and a bit difficult to carry around because the weight of the canister. Attachments are very well built and so useful, but the plasti materials used for the machine and the dolly seems to be a bit weak.
So in my opinion there are better machines, but I relly love it, the performance is excellent and really cleans the air. I also has 6 variable speeds and the bin holds more water and dirt than other ones.
I never used the newest model, but saw it on the web and I seems quite appealing, they reduced the size and the noise of the machine and introduced a remote control, a digital motor, a UV light above the water basin to kill dust mites, and it uses a separator, so no filters and baffles there! I just hope that they used different matterials and not the cheap plastic that they used to use.
Well, here are my two cents, hope it could help you
Kevin.