I've heard that compact flash readers allow your computer to much faster read the photos off the camera, than when you connect your camera over USB.
Is that true? What about other card formats, like SD?
My last camera only connected at USB1.1 speeds, so was slower than using a USB2.0 card reader.
However, if your camera can do USB2.0 or you have a USB1.1 or USB1.0 card reader, you wont see that benefit.
You can get Firewire or ExpressCard card readers for CF cards, which are faster than USB2.0, (and I think generally limited by the speed of the CF card). Sandisk do the fastest of these - see Extreme Firewire Reader and Extreme Pro ExpressCard Adapter.
Of course with USB3.0 devices beginning to appear, these are (theoretically) faster still than Firewire - but you need a machine that supports them (rather than running in USB2.0 backwards compatibility mode) to benefit from this speed.
If you don't want to drain your battery every-time you transfer the files from your camera, then you should use a card reader. Directly connecting your camera to the computer to transfer pictures, drastically drains the battery.
This depends on a number of factors but, in general, it would be true. The primary reason is that many readers are not attached via USB and so are not limited by the speed of the USB bus and are also not sharing the bandwidth of the USB bus with other devices. However, if your CF reader is USB, it wouldn't likely be much faster, if at all. Anyways, it can be all over the map and will very much depend on the speed of the reader, the speed of the computer, and the speed of the card.
However, a big win on transfering via a reader is that you don't waste your camera battery doing the download. Even if I wasn't gaining anything on speed, this is enough of a reason for me to not transfer via USB (though I do gain on the speed with my reader).