I use a Jabra Halo on my Macs.
I noticed that, when the Bluetooth keyboard, trackpad, magic mouse were all in use, the Bluetooth headphone did not work very well in Snow Leopard.
In Lion, when I connect the Jabra Halo to a Mac, the Mac reminds me to disconnect one of the connected Bluetooth input devices if all of the three are already connected.
It appears that a Mac supports only up to three Bluetooth devices. Is this true?