Utter disaster. (Man, shoulda gone with the REI Halfdome 2 or something else) Not life threatening but a royal pain. Took the kid (5" 9' 11 year old) and hiked the Chain Lakes Loop in the Washington Cascades (first hike for me in many years and first time for the kid (in the spirit of the Old Grey-Bearded One, I harass the kid alot but carried most of the weight and let him play in the snow and/or lakes as much as he wanted)). Out for three days and two nights. Walm days around high-seventies with nights in the mid-forties. (Gazillions of black flies and blood suckers but that's another story.)
Condensation City!! By the time morning rolled around on both days, anything on the floor on the inside edges of the tent were wet and every inside surface of the tent was soaked. Streams of water were running off. Sopping. Its small so you can't really avoid touching the inside of the tent. Everything dried out after the first morning only because we stayed there for the day and it was warm weather. It would have been a big disappointment to have to pack everything wet (including sleeping bag) in the morning and then unpack and use it wet that night. I talked to other backpackers in the area to see if it was (were?) the conditions but all had minimal condensation. I made sure nothing was covering any of the vents.
To make a short story long, it was a great first trip but not due to the Zeus EXO. Under these conditions, it is clearly the wrong tent and the highly vaulted (faulted?) Eureka "HI-LO" ventilation system failed. BEWARE. (By the way, I own two other Eureka double-walled tents and think very highly of them.)