2 months ago I purchased the top of the line flash for my DSLR camera, and I love it. It seriously changed the quality of my pictures, not only in low light conditions but also in bright day. The downside now, is that I have even more techniques to learn, and buttons to push! Though the basic operation is really simple.
The best feature of this flash is probably that it's orientable in any directions. So you can bounce the light and avoid the harsh light that direct lightning often produces. Most photos on my flickr stream are shot with this unit.
Today I noticed that the flash got a significant price drop compared to the MRSP and the price I paid! It is now $60 less than 2 months ago on amazon (free shipping, no sales tax):
When I got the flash, I immediately started playing with it, and it worked well for a while. But the next day, not only it suddenly stopped working, but it also hang my camera... Pressing the shutter button wouldn't work, flash mounted or not. I restarted the camera: no luck. I removed the battery and waited a bit: no luck.
The next day It magically started again to work, but meanwhile I had time to worry and I had contacted Canon. Canon support was amazing but didn't really provide a solution... except shipping camera's body and flash to Irvine, CA.
A couple of times, this behaviour came back, until I found the solution: I removed both batteries, including the one holding settings (date, time), and then the problem went away and never came back. Now I'm very happy with the flash. It makes a good christmas present, I'm almost tempted to get a second one at this price!