It's a clean air machine. The digital motor is in the top of the machine. If you read the first post, I explained the bag set up:
The bottom fill bags, I thought, were the dumbest thing I'd ever seen. Bottom fill bags!? What is this, 1974? But they work really well. Basically, if you imagine turning a Lux 345 on it's head, that's how it works - it creates a cyclone in the bag which forces the dust and dirt to the sides, keeping a clear air path through the middle of the bag. It also has a little cover which snaps shut when you turn the cleaner off to stop dirt falling out.
The bag is pretty full but there's been no suction loss as the dust is building up on the side of the bag.