As YOyoYOhowsDAjello mentioned, you do get audio support, but only by using a separate audio cable input - one of either of the two coaxial or two optical inputs. Not really a big deal for many.
The AVR-1609 supports the following audio modes -
Dolby Pro Logic IIx ? with Cinema, Music, Game Modes
Dolby Digital Surround EX Decoding
Dolby Digital Pro Logic II
dts ES Discrete 6.1 Decoding
dts ES Matrix 6.1 Decoding
dts Neo:6 Stereo-to-Surround Cinema and Music Modes
dts 96/24 5.1 for DVD-Video Processing
It does not support:
Dolby TrueHD
Dolby Digital+
dts-HD Master Audio
http://www.usa.denon.com/ProductDetails/4239.asp
Unless you have an audiophile speaker setup, you will likely not miss what it does not have. If you do have an audiophile speaker configuration, it is not likely that you will be looking at entry level receivers.
The AVR-1609 has a pretty good spec configuration, with the real value add of having a fairly full Audyssey implementation - it does make a difference you can hear once you set it up with the included microphone.
However, I still recommend that anyone with good speakers and an interest in playing HD-DVD and Blu-Ray go with what is arguably the real sweet spot in the Denon lineup, the AVR-1909, or even consider the AVR-2309CI / AVR-889 and other more fully featured receivers in the Denon line.
For what it is worth, I have the AVR-2309ci and am really pleased at how it works for both home theater and music.