As I understand it, most (if not all) digital SLR cameras have a buffer that will allow you to take a series of pictures while the camera is still writing a picture to the flash memory card. It takes time to write a picture file to the flash memory card. If the camera does not have a buffer, then you will have to wait until the camera is done writing the previous picture to the flash memory before you can take the next picture. Thus, the SLR cameras tend to have a buffer. The buffer can fill up with some pictures while the previous pictures are writting to the flash memory card. Thus, you will be able to keep taking pictures while the camera is writting to flash memory.

Now, the faster the flash memory, the faster the camera can write those previous pictures to the flash media.

Generally, it will not be much of an issue as long as you are NOT taking enough pictures fast enough to fill the buffer before previous pictures get written to flash media. Where it can be an issue is if you put the camera into rapid shoot mode and take a long sequence of rapidly shot pictures (i.e. at some thing like a sporting event). In such a case, you might fill the buffer up faster than it can empty the buffer by writting to flash media. This is where faster flash media can help. The faster the flash media, the faster the camera can off load the buffer to flash media and leave room in the buffer for more pictures shot in the rapid shoot mode session.

Thus, you will not likely notice it too much when doing general shooting.

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[soapbox] Backup good...no backup bad!! [/soap box]