re: Best Roomba for an apartment with hardwood floors & area rug?

How thick is your area rug? I've never actually tested my Roomba, but I think any rug under 1" should not be a problem

The Roomba's wheels are about 3" in diameter, and they actually can extend all the way out to let it climb over thick rugs.

Cleaning power doesn't differ much between robotic vacuums, no matter the model. There's a physical limit to how much suction power you can generate given the power a portable battery can put out.

If you are looking for a budget (relatively speaking of course, it's still quite expensive) robotic vacuum, I would go with the Roomba 860. It's the cheapest model you can get that still has the next-gen brushless rollers. I like them because the "brush-less-ness" makes cleaning hair out of the Roomba so easy.

If you feel like reading, here is a detailed review of the Roomba 860. About 2/3 of the way down, there is a picture of how the Roomba's wheels stick out.

I think Neato have even cheaper models but I would wait until they come out with a brushless version if you want to go that route. There's a lot of Neato fans here. :)