How is it compare to other robot vacuum?
No reviews 
@ Vik0dmk
A few months ago I got a Roomba 630 from Woot, described as " Condition Factory Reconditioned; Open Box " for a little less $ than this 675.
This 675 appears to be very similar, but maybe the next step up.
I would not hesitate to buy the 675 at this price based on my experience with the “entry level” 630.
Be aware that there are not a lot of features like on the more expensive models, althought his one can be operated with your phone (my 630 cannot, it is the most “manual” robot you could imagine lol).
My 630 says it will dock itself but it does not. I have to search for it and take it over to the dock myself, but that is okay with me - I just like that it runs while I am out and goes under the beds and stuff plus does a remarkably good job. Sometimes I just close it in one room at a time and leave it in there until the battery runs out. I imagine if you have previously had a fancier robot vac, the 630 and likely the 675 would not be satisfactory with so few features. The fact that the 675 does not self-adjust for height might be a concern but I only have hardwoods so it would not matter to me.
For what it’s worth, when you split a username from the at symbol, they don’t get a tag notification. Though since you replied to the post, they would be notified.