There are certainly plenty of compact megazooms to pick from these days, but the Samsung WB850F stands out for a few reasons.
Its 21x zoom lens starts at f2.8 23mm, making it the brightest and widest lens currently available on this type of camera. It has a brilliant 3-inch high-res AMOLED display, which works well even in bright sun, and Samsung's Smart Panel user interface (also found on its higher-end ILC cameras) letting you quickly change important camera settings from one screen. And then there's the Wi-Fi.
The camera's built-in 802.11n wireless can be used to connect to your Wi-Fi network for automatic backups to a Windows computer or Microsoft SkyDrive, viewing photos and movie clips on DLNA-equipped devices, or sending them by e-mail; to connect to other Samsung Wi-Fi cameras for direct sharing between cameras; to connect to hot spots or wirelessly tether to a smartphone; and to connect directly to an Android or iOS device.
That last option can be used to send photos to your phone for viewing or uploading to sharing sites, but it will also allow you to control the camera remotely. (Samsung only guarantees these features to work on Samsung Galaxy devices, but I was able to use them on other Android devices as well as an iPad 2.)
There are a few shortcomings, though, such as mediocre battery life, and the camera is more about filters and effects than producing great-quality photos and movies. But, hey, they're plenty good for online use and there's really nothing wrong with that, especially considering its shoot-and-share capabilities.
The Samsung WB850F's picture quality is very good for its class. Like many point-and-shoots, the more light you have, the better your photos will be. If you're considering this for daylight shooting, you'll likely be very satisfied with the results.
Subjects do get noticeably softer as you increase ISO, which means with less light you'll lose sharpness and fine details, and things start to look flat. (They definitely benefit from some light post-shoot sharpening.) On the other hand, the f2.8 lens and the back-illuminated CMOS sensor keeps the camera from immediately ratcheting up ISO, so you can take low-light photos (at least at the wide end of the lens) with better results than some competing models.
Basically, if you're considering this for its online-sharing capabilities and don't typically make large prints above 8x10s, regularly enlarge and heavily crop pictures, or view them at large sizes on screen, it's a fine choice. You can read more about picture quality and shooting features in the slideshow above.
Movie quality is about the same as its photos. Shoot in good lighting and you'll get decent sharpness and detail (though the camera's dynamic range limitations are more pronounced), but the less light you have, the softer things look and artifacts are more noticeable.
The zoom lens does function while shooting. It can be heard moving while recording, but Samsung includes an option to damp the audio when you zoom. The continuous autofocus can be slow to adjust and may pulse in and out of focus, so it might be best to zoom in first and then start shooting; you can always pause the recording (yes, the camera lets you pause) and zoom out and start capturing again. Also, though Samsung is able to correct for barrel distortion in photos, it doesn't for video.
Going by my lab tests, the WB850F is neither exceptionally fast or slow for its class. From off to first shot took on average 2.4 seconds, and you're waiting roughly the same amount of time from shot to shot. Using the flash doubled the wait to 4.8 seconds. Shutter lag -- the time from pressing the shutter release to capture without prefocusing -- is reasonably low in bright lighting at 0.4 second, slowing down to 0.7 second in low light.
The camera has a maximum burst shooting speed of 10 frames per second at full resolution for up to eight frames, which it was able to hit. However, that's with focus and exposure set at the first shot, so if you have a fast-moving subject, it might not be in focus for all of those.
Out of the lab, the camera's speed is a little less reliable. For example, if I tried to take too many shots in a row, the camera would stop responding for a few seconds. That's likely because it was busy processing images, but it can definitely cause you to miss the next shot.
Like many megazooms, the WB850F's AF slows down some with the lens extended, which is particularly noticeable in low light, and the camera seems to lock the zoom lens for several seconds after taking a picture, meaning that you can immediately zoom in or out. Also, while the burst capabilities are good for catching an action shot, once you release the shutter, you're stuck waiting for about 2 seconds per photo before you can shoot again.