We have an earlier model roomba. I can't say anything about later models, but here's what I've learned from mine:

It works great on smooth-ish, hard surfaces, sweeping up dirt and bits of dried mud and pet hair and cheerios, stuff like that, but if it's a pile of dirt big enough for the casual male eye to notice, get out the broom and dustpan, ya wuss! 

Rugs? Not so much. Ditto, carpet. Damp, wet, or soggy? Uh, no.

It WILL find and munch on any wires, shoelaces, articles of clothing, and/or ...err...organic matter left on the floor. 

Battery life? Meh. A half hour, then it has to take a smoke break while it recharges. 

Take the danged thing outside when you empty the dirt trap. All it takes is a little fumble and whoopsie!

So, it works, within its limits.