The only thing I heard bad about it was run time was really short. Like 10 minutes on a 5.0 battery and 5 minutes on a 3.0
I've gotten around 11 minutes on a 4.0 battery (and 9ish on a 3.0). The 5 minute runtime would be on the smaller packs. The M18 vacuum really needs the XC packs. Anyway, you're not cleaning a whole house with it.
The filter on this vacuum is EXCELLENT! It's a gore style washable wet/dry filter. I picked up a shop-vac foam pre-filter to wrap around it for easier cleaning (I had to cut off a couple of inches to make it fit). Something like this:
http://www.amazon.com/dp/B00002N6RY/?tag=atomicindus08-20
Suction is pretty good, Not shop-vac performance, but that's only because the hose is so much smaller. But it truly does have the suction comparable to a household vacuum. It's louder than my wife's Kenmore vacuum though, and MUCH louder than my Fein (though that's a hardly fair comparison, because you can have a quite conversation over that). But it's not as loud as a typical shop vac, so noise level is acceptable.
But the fact that it's entirely self contained is the best part. Its great to just grab the vacuum, and start cleaning. No fumbling with cords to plug in or put away. No searching for an outlet (and moving around stuff to get the cord in without toppling a lamp, etc). No worries about finding all the accessories. I had a dishwasher that caused a flood, and this was just a pleasure to use to clean up.
One thing I find missing. A brush nozzle. I picked up one of these at Sears:
http://www.amazon.com/dp/B00002ND49/?tag=atomicindus08-20
and I am able to just fit it inside, though there is no clip for it.
One note. Like a typical wet/dry vacuum, there is a float ball under the filter that prevents water from being drawn through the motor if you overfill the tank. But when dry vacuuming, if you tip or move the machine too much while it is running, the ball can bounce up and stop the suction. You then need to stop the machine for the ball to fall back down. There's nothing wrong with this, but it can be disconcerting if you're not expecting it.