For me, price is huge followed by the number of Inputs and outputs.
The ability to scale resolution of the output signal is also really great, however this really depends on the quality of the scaler. Will I get better scalling by changing the output of the origional source?
I'm not as concerned about audio connectivity as I would really want to drive my projector with the HDMI single (only Video). However, as there are limited recievers that support HDMI switching internally, having audio connectivity and putting this switch between the sources (DVD, STB, etc...) and a HDMI capable reciever so you can then select between multiple HDMI inputs (while only using a single input in your reciever) would be very nice as well.
Mike