While the shape and attitude of the Roomba remains the same, much of its anatomy is changed. The most obvious improvement is its dust reservoir which is now a single easy-to-remove piece. You pop it out, pull out the air filter and empty both over the garbage. (Before, these were two separate hatches on the Roomba's body, so you ended up shaking the whole vac over the garbage and making quite a mess.)

Roomba can now dock itself in the battery charger when batteries are low. The talent is limited, however— it can only get to its dock if it's already within five feet of the thing. Guess who has to pick it up and place it within five feet?

The third major enhancement is the Dirt Alert sensor. Probing the floor for a high concentration of dirt particles, Roomba makes additional passes in the dirtiest areas to get it all up before moving on its path. Combined with the "Spot" cleaning function introduced in the last generation, this feature amplifies Roomba's role as an expensive DustBuster buster.

After putting the Roomba Discovery through the paces, I felt a little let down. I guess I wanted more overall performance improvements. Not only does the latest get hung up on the same wires and rug fringe that its predecessors did, but it still has a haphazard way of covering the floor, never sure where it's been or where it's going. No matter what room I let it get to work in, I still have to come to its aid, and when I dotted certain parts of the floor with carpet freshener, I noticed that after quite some time, some of my dots still hadn't been touched.

I'm still waiting for the killer Roomba, upright and intimidating, with a full-size bag and a processor that can map a room with precision. My dream Roomba would also have to have a retractable nozzle for cleaning corners, something today's disc-shaped model just can't reach. Until then, sadly, I'll have to do it myself.