As requested by @dirtbaghiker, I’m giving my 2 cents on the Hilleberg Saivo. (I feel kinda naughty posting about a 11lb tent on the backpacking LIGHT forum ^_^)

We just used it during our attempt at Mt. Whitney. It was definitely overkill for the conditions there–we were below the tree line and in non-storm conditions. This tent is really designed for expeditions where you must be prepared for the most extreme weather.
The tent is heavy at 11+ lbs and requires a large clearing to pitch. We pitched it on what was the road leading down to Whitney Portal Campground. Not only does it have a large footprint, it also requires even more area to be guyed out properly. And yes we should use every single one of the 24 stakes if we want to make Bo Hilleberg proud. Alternatively, we brought a set of 18 snow stakes for this trip as the included Y stakes won’t cut it in deep snow.

We used the front windward vestibule for our two packs and the rear, leeward one to cook. The inside was spacious for 2 people. The length was just enough for my 6’2 hiking buddy. His down hoodie and bottom of his quilt were touching the inner tent though. We had our bear can, waters, and other items between the two sleeping pads and other personal items on the other sides. Each side has 6 pockets so it’s storage for days.

Besides the weight and space required, the drawback to this dome tent design is that with the vestibules open, snow and condensation will fall into the inner tent because of its sloping roof line as well as a slanted inner tent door. We found that we had to hold the inner tent door up and knock off the frozen bits from the outer shell and top of tent to prevent ice / snow from falling in. The trick we found was to open the inner tent door opposite the side of the outer tent door to compensate for dome geometry.

If I had to do it over again, I would most likely get the Kaitum 3 as a much lighter and spacious alternative to the Saivo for our SoCal winter trips. The tunnel tents have vertical inner tent doors covered by a little bit of the outer tent lip. They also offer more vertical space and less poles to put up. I wouldn’t mind giving up some of the bombproofness for space, comfort, and less weight. Nothing beats the geometry, aerodynamics, and stability of the dome shaped Saivo, though.