For Christmas 2016 my boyfriend and sister got me the open air Litter Robot for my cat. My sister already had one and loved it. I couldn't get past the pricey cost of $395 but they swore it was so worth the money. THankfully they got it for me, and yes it is worth every penny.
While it does take up a bit of room the item self cleans, and there's no smell (unless you open the waste tray). I've only had it for a week and a half (today is January 4) and I have yet to change the waste bag.
My 9 month old cat took to it after a few hours, and he's been using it ever since.