Canon has managed the tradeoffs between form and function well in this camera. There are some small things I would have done differently, (zoom control and flash) but I can live with them the way they are.
On the plus side:
Firstly, one has to comment on the massive optical zoom in this tiny body - 12x optical in a compact of these dimensions is a rare achievement. Most compacts are in (or below) the 5x range, so this is something special. The zoom has wonderful reach and the Image Stabiliser handles most camera shake well, even at long zooms. The build quality overall seems solid and what you'd expect from Canon.
At 12.1 Mpix, you can print photos the size of bath towels and have them look sharp, so there is more than ample MP for most uses.
Another seller for me is the inclusion of HD video, something Canon was slower than the competition to put into their cameras, but great that they've done it now. One thing to note - you can't use the optical zoom in video mode - only digital. This is great because zooming is completely silent, but not-so-great because you only get 4x zoom, so be sure to adjust your optical zoom before you start your video recording. Video quality is good, it uses loads of storage space though, so get a huge SD card (or 2) when you buy this camera. Oh, and make it a fast card too, an Extreme III for example - it makes a big difference to overall camera performance.
Lastly, there is no optical viewfinder, but the large LCD screen makes up for it, and does well even in bright light.
Otherwise, the camera is typical Canon, menu structure and controls are well laid out, the scrolling wheel is new, and helps to navigate menus and options, I still prefer the good old directional click, which is still available, but I can see the scroll-wheel being important for some people. Face recognition is nice to have, and works well. There is no RAW recording capability here, but I see that canon has released RAW for some other cameras in the SX series, so, who knows, maybe in a future software release. I've been able to achieve some nice effects with the camera, the images are sharp, sometimes a little too saturated, and it delivers decent bokeh, mainly due to its zoom ability - the lens is not an especially fast one (f/3.4 - f/5.3), but then again, that is not to be expected in this class of camera, and it's fast enough, even for most low light conditions.
On the negative side:
I don't like the flash implementation in this camera - well, specifically the way you can't control the flash pop-up. When you switch on the camera, the flash comes up and that's it - there's nothing you can do about it. I hold it down to keep it out of the way. There are rumours that Canon will fix this in a firmware update, and I hope they do, it's a significant design fault in my view. Also, on occasions where the camera is in use and the flash takes a bump - I can see it snapping off, or getting damaged - it's not especially sturdy, and I take good care not to damage it. (all the more reason to have it only show up on command)
The other niggly thing is the grip on the zoom control - I find it hard to get hold of, especially when I need to make fine adjustments to zoom length, this is a minor gripe, but adds a lot to the usability of the camera. I would like to see the zoom grip more prominent on the camera - there is space for it in the form factor and within the design too.
Overall - a lovely camera, powerful, functional, long battery life and should do well in most circumstances. Delivers good quality images, HD video and new features like face recognition and some others not mentioned here do a good job. If a versatile compact is what you're after (and that zoom!!) and you can live with an unruly flash and fiddly zoom grip, I would strongly recommend this camera.