I'm 65 and partially disabled from a stroke. I cant use a regular vacuum so Roombas have been a blessing for me.
I have a lot of Roombas (one is too many and a dozen wouldnt be enough for us addicts) from the basics to the most expensive -- and, believe me, the 400 / 4000 Discovery models work better than the newer, fancier models.
I've bought a few Roombas from the iRobot site. But then I got smart and started buying them on eBay. Most of the ones I've bought on eBay were refurbished but they worked right out of the box just as well as the new ones. I also buy the batteries and other supplies on eBay.
http://www.ebay.com/sch/i.html?_nkw=...4&_sop=1&_sc=1
If you're nervous about buying on eBay, you can also check out Roombas on Amazon:
http://www.amazon.com/s/ref=sr_nr_sc...rnid=386465011
I ended up with a lot of "walls" but never use them. They might be useful if you want to vacuum only a portion of a room. Instead, I just close a door or put a chair or rolled-up area rug in the doorway. The Roombas are very respectful of objects like that.
Edited to add that the above searches are my own. You may be able to find better deals using other search terms. You can also google
BUY ROOMBAS and find some good deals at sites other than iRobot.
Edited to add, also, that the older models seem to be easier to change out the batteries than the newer ones. I like the Discovery models and older ones where you just turn the Roomba over and flip out the old battery. Too, if you buy on eBay, be sure to look for sellers with a 99+% rating. I've been buying on eBay for 12 years (4,000 purchases) , dealing only with sellers who have that kind of rating (98% is not good, in my opinion) and havent had a bad purchase.