The Soulo is not replacing the Unna. It is a more minimalist version of the Staika, with 3 poles crossing at the top and a small vestibule. I have tried out an Unna, and though it does not have a vestibule, one of the corners easily detaches to allow the user to create a vestibule if desired.
The Unna has two crossing poles, the Soulo three.
Unna has pole sleeves, Soulo has clips.
Unna has a rectangular footprint, the Soulo looks more hexagon-ish.
Stats (inner sq ft, vestibule, total sq ft, height, min wt, max weight with stakes/stuff sack)
Akto (18.3, 8.6, 26.9, 36 in, 2lb 14oz, 3lb, 5oz)
Unna (27, 0, 27, 40 in, 4lb, 4lb 7oz)
Soulo (21.5, 7.6, 29.1, 38in, ?min, 4lb 10oz)
Jannu (36.6, 13, 49.6, 40in, 5lb 8oz, 6lb 3oz)
Opening US price on Soulo, $525. Ouch! I suspect all the tent prices will go up with the 2008 catalog.
For those not familiar with the manufacturer, their tents are bomber, the organization is smallish with great customer service, and the tents are handmade with the name of the person who assembled it stitched onto a seam. Their tents are far from ultralight, but are on the light end of the expedition spectrum, for use in climes where you aren’t going to bring a tarptent.