Don't bother with any Roomba below the 800 series or almost all of the knockoff designs because they still use brushes. Cleaning the brushes SUCKS. The Roomba 800/900 and new E6/i7 series all have rubber rollers that require almost no maintenance and clean very well. Also, because they use the rubber rollers, cords aren't a problem on the newer Roombas while they are an issue on any robot vacuum with brushes, which is all roombas under 800 and most of the knockoffs.

We have the i7+ that empties itself and frankly it's dumber than the 960 we have in the back of the house, so for the price bump I can't recommend it, although the wi-fi strength mapping you can turn on in the app is informative about where the high and low spots are in your house for wifi. You should be able to get an 800 series one for $270-$300 on sale and a 900 series for around $425. Costco has the E6 now for $325, but I have no experience with that model. It should have rubber rollers.

You can get a near top-of-the-line Roomba 800 series for about $300. No one is going to vacuum your house every day (it always surprising how much crap it pulls out of our carpet every single day - carpet is a DIRTY flooring choice) for less than $1, and that's just year one. They typically last at least 3 years on the original battery as long as you change the filters and do annual maintenance.

You must be extremely hard on your Roombas or have been buying the crappy 500/600/700 models. We usually get about 3 years out of them before the battery has to be changed out (which is when we usually replace the battery then sell it to get a new one), but we change filters regularly and do maintenance as required.

The sensor already exists, so it's just a matter of time until one of the vacuum robot manufacturers integrates it.

In the initial days you had to set the roomba down in the room you wanted to clean and manually start it, so you were generally aware if there was dog poop around. However, once they made models with unattended scheduled cleanings, the problems started in houses with non-house trained or accident-prone dogs. The existing sensor will fix this, it's just a matter of who implements it first.

The E6 or i7 (no plus)?

The 960 is 4th from the top now. i7Plus->i7->980->960->E5/6.

That said, the i7 is nothing to lust after, at least not so far. It's much dumber than iRobot marketing wants you to believe. Just the tiniest of improvements over the 960 (though the i7 is MUCH quieter than both the 960 and the jet-engine 980).

That's a garbage robot because it's knocking off the ancient Roomba tech that used brushes. They are a PAIN to clean. The newer Roombas use rubber cylinders and stronger suction instead of brushes. This requires WAY less maintenance and less failures.

Basically don't bother with any roomba or roomba knockoff that uses brushes. And if you are looking at a knockoff, make SURE it is UL listed. Lots of chinese junk isn't but look like respectable clones that will set your house on fire when you're away because of a battery short or some other quality issue.

You can get a Roomba 960 for about $300 now on sale. I'd look for that. You might THINK you want a 980 for the better suction, but it's an order of magnitude louder than the 960. We had both and we still have the 960 (and an i7+) but the 980 is long gone because of the noise. Stay FAR AWAY from the i7 and i7+. Roomba abandoned that terrible platform after less than a year and replaced it with the S series, but you still see the i7s on sale.