So, I've had my Roomba 535 for two days and I am in love with this thing! I have terrible dust allergies and when I vacuum I am miserable for hours after from the dust it stirs up so I don't do it nearly as often as I should, considering I have two cats. I ran the Roomba yesterday and I cannot believe the amount of cat hair it picked up. It did an unbelievably good job.
It's as good or better than my current upright vacuum, which is a beast of a thing with lots of power. All in all, so far, I have never been this pleased with any purchase I've ever made. I had high expectations for it, and it has more than surpassed them.
I got it from HSN.com for $249.90, with a 15% off coupon code I found on retailmenot.com(another great, recent discovery) so it came out to $212.42. HSN lets you split it up into 4 monthly payments, so it's great!
Anyway, if you've ever considered getting a Roomba, the new 500 series is definitely worth it!
(Unfortunately I'm not getting paid to say any of this, I'm just REALLY impressed.)