960 and 980 not ready for primetime, save your money on a lesser model.
Roomba does not live up to expectations, and the major benefit of paying for the 900 series does not in fact work reliably. Let me start by saying I was a very happy Roomba user for months. It worked flawlessly. Then iRobot flashed the firmware and obviously made significant changes to the logic handling charging. Prior to this update, my Roomba would return to home base to recharge with about 5% of the battery remaining, and it reliably made it to the charger, recharged the battery completely, and continued the job. During a normal cleaning cycle in my house, the Roomba would return and fully recharge the batter twice. This would result in a a total job time of around 5.5 hours, and a report showing about 2200 sq ft cleaned. Immediately following the update, the Roomba would wait until approximately 1% remaining batter prior to returning.....so about half the time it wouldn't make it to the recharger. If this happens, the job cancels,you have to manually put it on the charge, wait until it's charged, and restart the job. If it did by chance make it to the charger.....it would only charge the battery half way before restarting. This means that it would then return to the charger in half the time. Now it would take 5 or 6 trips back to the charger to actually complete the job. It almost never made it through the whole job, as it would run up against the depleted battery, die before making it to the charger, and cancel the job. I bought two new replacement batterries, and the problem remained. I inititiated a support request. Suddenly, after dealing with the charging issue, the Roomba started having more issues, like going in a circle or returning to the charger immediately. Support first sent me a replacement wheel, which did not help, then decided to send me a new Roomba. Well, they sent me a 980, and directions to put the battery from my 960 into it. That didn't work at all, the new Roomba was worse. New support request, they had me send it back, then told me the issue was that the 960 and 980 had different batteries...that was the first I'd heard I got a 980 replacement (they look identical). So they shipped me another new 980, AND a new 980 battery. The new Roomba ran great, finished a job, I was happy again! Ooops, soon as it phoned home, it got the latest firmware upgrade and.....BAM. Now the new one is doing the same thing as the original 960. So here I have nearly a thousand dollar piece of high tech gadgetry, that was purchased for the sole reason that it could recharge during a job, and continue the job..........and now that function doesn't work. I now have essentially what I could have gotten from a different brand for under 200.00.
In addition, the 980 is supposed to have a much stronger motor and perform several times better...this in fact does not seem to be the case. Instead, the motor goes into "turbo" mode which basically appears to mean it gets noisier, and nothing more. Based on these issue, I would strongly recommend that you do not spend the money on either the 960 or 980 if your primary reason for purchase is the "return to charger" function.