If you get an HDMI 1.3 pass-thru receiver you won't get the benefit of HD audio in any way, because the signal just passes through the receiver to the display (which won't be able to utilize the HD audio it is receiving). "Don't get pass through or a lot of things won't work because of the repeater architecture of the HDCP codes"
HDMI repeater passes audio (blu ray), HDMI switcher doesn't, HDMI passthrough is where the signal isn't touched, it's just passed straight through the reciever. As far as ver. 1.2 repeater or 1.3 passthrough, it really doesn't make a difference.
A repeater is more complicated. Repeater is a concept borrowed from computer networking technology, and could repeat (with amplification), switch, distribute, duplicate, or protect the signals.
A simple repeater has a small amplifier that can be used to extend an audio or video signal beyond the standard length specified for the cable.
A repeater that acts as a switch will take input from a multiple sources such as two DVD Players and send it one device, such as a TV. Irrespective of which DVD Player you use, you will be able to see the image on the TV.
A repeater that acts as a distributor takes input from a single device such as one DVD Player and sends it to multiple devices such as, say, TVs. As a distributor, only one output device will work at any one time. If more than one device is to be active, the repeater can also act as a duplicator.