I've owned trilobites for a good while. the object avoidance is second to none (STILL! after all this time). I now own an XV-11 as well, and I feel like comparing the two.
*round (doesn't get stuck in corners, can turn around anywhere)
*heavy / well balanced (suspension doesn't cause it to climb up stuff / negates roller hop)
*silicone wiper seems to last a long time, and doesn't fill with hair too fast
*beater bar has helical slots (no "beating" noise)
*can "see" everything. I mean everything - it avoids plastic bags, (beverage) glasses, boot trays, etc.
*very effective dirt pickup
*HUGE dustbin (for a robot vacuum)
*Knows how tall it is (it can "see" if it has clearance to go under stuff)
*won't fall down even the most devious of edges (I have a carpet that ends 2" before the stair, it won't fall over it)
*very "refined" movement - appears more graceful than frenetic - seems to know if it's not moving
*top shelf fringe / cord disentanglement logic.
*quiet drive system
*no real nav, complex room layouts confuse it
*can get into areas that confuse it, and not leave
*sometimes runs into corners (sonar gets reflected away and it can't see them)
*dustbin sensor is rather useless
*they don't make it anymore
*Obviously, the navigation. it can do the entire first floor (5 "rooms"/areas), without much stupidity
*time/power efficiency - also thanks to SLAM
*good cleaning power (sucks up fur like nobodies business)
*support! (both software & service)
*Has no idea how tall it is, can't figure out object bases (like 90% of floor lamps)
*climbs it's butt up stuff (and can scratch stuff with the charging contacts)
*the turret needs a proximity sensor (it likes to whack into stuff that's just taller than the laser port)
*falls down the more devious edges (I have a high-pile carpet that ends 2" before the stair, it sees the little drop, keeps going, then sees the stair drop, attempts to stop, and because of the suspension (& physics), stopping causes the tail to lift a bit, and over it goes)
*doesn't know when the dustbin is full (I have two dogs and a cat - I usually start it, then empty it after the first 10 minutes as it is already full) and will continue to run for a full hour with dirt packed roller (yes, It is scheduled to run 7x a week).
*non-helical beater bar makes noise, causes front end "bounce" on certain surfaces. (yes this was basically addressed with the pet version)
*fringe logic still needs some work - mine has damaged it's toothed drive belt (shaved off a few teeth)
*overall situational awareness (as it appears to a human observer)
Overall the neato is a fantastic product, both for it's cleaning power, and it's ability to clean large, complex areas. If I could gift some of the ZA2's abilities to it, it'd be virtually perfect.
I might was well list those here.
So what is the ideal vacuum? In my opinion, a trilobite ZA2 (for the refined design/construction, movement and object awareness), plus neato's laser SLAM, efficient nav/pattern & scheduler. (this could probably be managed within a reasonable physical container)
if you wanted an beefier / industrial version (I wouldn't mind), add a karcher style base, and cyclone filtration (it's getting bigger and power hungrier now).
if you wanted to go really nuts (yes please), add wifi and a kinect camera to the above, & offload the processing to a networked computer. Of course at this point it's now the size of a robot lawnmower, but I can dream, can't I?