ExecSum: This is a really fun camera. It makes taking pictures really easy.
Background: Those unfamiliar should peruse a website (such as this one: http://www.kenrockwell.com/canon/s90.htm) and get familiar with the features.
Evidence: These videos (http://vimeo.com/8819603, http://vimeo.com/8447361) were both made with my S90.
-Small, fits comfortably in a pants pocket
-Intuitive features and access to them. The dual rings rock.
-Fast lens. (f2!)
-Big, sharp screen.
-Very nice video. The mic is shockingly sensitive.
-Intelligent auto-focus (except at short distances).
-At distances of less than 8" the focus is very fickle. (even on manual)
-Cycling between shots is slow.
-A bit slick to hold.
-Secondary (screen-side) function ring is small enough that manipulating it with gloves is very delicate at best. It's easy to inadvertently trigger functions in certain modes.
-Lens ring could be more responsive (ie, twists should change settings faster)
Most of my use of this camera was on a two week trip to Egypt earlier this month (see video, above). For most of the trip, I kept the S90 in the front right pocket of my pants. With a combination of easy access and discrete appearance, I got countless shots and video clips that I wouldn't have otherwise. A big camera stuffed in a bag is hard to grab quickly, and looking like a tourist causes people to act like you are. Both are to be avoided. The same things obviously hold true in the backcountry.
Being able to set and forget the ring functions makes the camera extremely user-friendly. 95% of the time I shot in aperture priority, with the lens ring set for manual focus, and the screen-side ring controlling the aperture. It takes little practice to manipulate both simultaneously.
I think I'll have a bunch of fun with this in the woods.