The Canon 7D has two types of continuous shooting mode: High speed continuous and low speed continuous. What are the practical applications (scenarios, photography style, uses, etc) of using the low speed continuous mode?
My camera has high speed 6.5 fps and low speed 3 fps. I use 3 fps most of the time. This is good for normal slow situations of people. 333ms is enough time to allow facial expression/eye blinking to change between the shots. 6.5fps is just way too fast and I fill up my CF card too fast and sorting the photos in the end will waste too much time. So I consider slow speed to be default and high speed for special occasions.
Highspeed is useful for fast action, like animals running fast and catching a ball in the air, or sports where you want the exact moment the soccer player hits the ball, or the puck in hockey flies past the goalie's head and he looks surprised, or a horse jumping the tallest hedge, runners touch the final goal strip, etc. Or maybe you just want to make a stop-motion-like film of a phenomenon.
The main advantage is easier continuous shooting over an extended time. Generally, continuous shooting goes in to a buffer and eventually that buffer fills. When shooting high quality RAW images particularly, that buffer can fill within 6 to 12 shots on many cameras. Even my 5D Mark III fills the buffer (with two very high speed cards) in about 17 shots at top speed.
By shooting in a slower mode, the shooting is easier to control and can also run continuously for a longer time since the buffer is filled more slowly. It also may be a quieter shutter. On the 5D Mark III it is continuous shooting, high speed continuous shooting and silent continuous shooting. Silent goes the slowest, but has a quieter shutter, continuous fills in the middle and high speed is like a machine gun. (Ok, not quite, but you get the idea.)
The most common reason for me to use that mode is when I think I may want to get a couple of shots in a row, but I don't want to accidentally squeeze off two or three shots when I really only want one. At 8fps, the shutter is really sensitive, and it's really easy to wind up taking extra shots unintentionally. I used to experience that even at 6.5fps on my 40D.
The low-speed continuous mode, on the other hand, is slow enough that I only get multiple shots if I'm deliberate about holding down the shutter, so I'll use this mode for casual snaps, candids, and so on. In most of these cases, I'm just shooting one frame at a time, but if there's a reason to capture more than one, I can.
Sometimes the 8 fps of the 7D is a little faster than you want to go in burst mode. Even with the Version 2 firmware, you can fill the buffer in about three seconds when saving to RAW files. By reducing the frame rate to 3 fps you can stretch that to around 8 seconds with a fast CF card.
I shoot a local high school band. During their halftime show at Friday night football games I sometimes want to shoot a stop action sequence for use in a multimedia presentation at the end of the year. I prefer the slower rate for this as it makes it obvious it is a series of stills, even when played back in real time. The 8fps looks more like slow, jerky video. An eight second sequence also allows me to capture an entire move such as a spinning toss and catch of a flag, rifle, or saber. Since the lights in the stadium pulse at a slower rate than the Tv I need to freeze the action, I need to use RAW format to correct for the changes in WB and brightness from frame to frame.