No one else has responded so I'll give you some input...
I'm 5'10" 160lbs sz 9 boots.
I had a 2013 Ultralight 163 last year. It's hard to give impressions without back to back comparisons but I had a two board quiver before the Ultralight...a Salomon Sick Stick and a Burner. It turned out to be the perfect replacement for the two. In powder, I do remember getting slight leg burn first morning out...but the board wants to charge so as you start going faster, all that goes away. Its a relatively soft board and damp so it really felt great in the crud and handled moguls very well. The board seemed to handled carving on hardpack very well, good grip. It could be just a great sidecut or it could be the Ultimate Grip feature from 2013. I liked the feel better then the 7M Magnetraction I have now. Grip felt far superior to the Salomon boards. Definitely stable at speed...right there with the Burner which was a fast board...but much easier to turn and rode short with the hybrid camrock.
For more comparison, this year I started on a Rossignol XV Magtek 163...stiff board, big setback. I remember thinking when I first rode it...this is way more work. Not as maneuverable in tighter trees, harder in moguls, not as damp...was hard to ride all day. You really have to work the flex this board. After 20 days my fitness and riding has adapted to the XV. It no longer feels clumsy. The base is not as fast as the Ultralight but it's even more stable and just wants to go straight down everything all the time.
If you are even thinking about a board like the Ultralight, I bet you will really like it. There may be something even better but we would be splitting various shades of excellent. As a top end freeride board...I doubt it could really disappoint anyone. It does cost a lot and my Tunisia built 2013 had quality issues and I warrantied it in the end. They are now being build back in Switzerland.