Are these really necessary?
You can have sound
OR
you can have optical zoom.
Two "features" included with the SP-550 against which I'm personally biased are digital zoom and video mode. Digital zoom adds a faux 5.6x power to increase the "zoom" to 100x. But digital zoom adds nothing to the image that proper post-processing couldn't handle better after the fact. The image stabilization did not appear to work (or work well) in digital zoom mode. I attempted several long shots on a reasonably bright day and they were quite blurry from handshake.
Additionally, I understand why some want video mode in a still camera and Olympus has answered the consumer call. However, with the SP-550’s video you are forced to make a choice. You can have sound OR you can have optical zoom. You cannot have both. If you choose sound, then you are allowed to use the digital "zoom" to augment the optical zoom at which you started shooting (you can set the optical zoom before recording, just not during). I presume this is because the optical zoom mechanism is so noisy and near the microphone, that zooming would effectively ruin any sound captured.
The auto focus was slow to adjust to changes in subject during recording as well. Just as video cameras typically take horrible still shots, this once again proves that video recording is best left to video cameras and still shots to still cameras.
Drive mode
15 fps mode is only available at 1280x960
(and lower)
One of the most anticipated features of the SP-550 was the ability to capture up to 15 frames per second in burst/drive mode. Tainting that promise is the fact that High Speed-2 15 fps mode is only available at 1280x960 (1.2MP) resolution and lower and the maximum frames captured in a sequence is 20. One nice feature of this burst mode, however, is the Pre-Select option which captures five frames when you half-press the shutter, acting like a TiVo buffer. This enables you to "capture the moment" you wanted even when your reflexes and prediction ability are not on par.
The other drive modes are High Speed-1, which captures 3MP images at 7 fps with a 15 frame maximum and Normal mode, which captures full size 7.1MP images at 1.2 fps up to 7 total. I was disturbed that the LCD blanks during drive mode making it impossible to track a moving subject.