Canon more or less invented the pocketable, fully controllable digital compact market with the Powershot S series, but they rather lost their way with the S80 - where was the RAW support? - and then forgot about this area. Until now. The S90 catapults them back to top of the class, with a truly pocketable camera capable of excellent results - for a compact - and a fantastic amount of user control. And also a great system of controls, designed to appeal to experienced photographers - even those pining for the days of mechanical cameras and film.
Downsides - it's noisy at high ISO levels. No optical viewfinder.
Plus points - just about everything else. A jewel of a camera.