Might have some overscan issues too, but is OK
I have a Mac (desktop not notebook) connected to my 58" Panny Plasma via DVI to HDMI. Picture is great, but getting the picture exactly centered has been a challenge. I am using the 8800GT video card. The four corners overflow a bit so the Apple logo is obscured a tad, the menus are obscured a tad, etc... Right now, the Macs lack a way to control over/underscan out of the box. I left mine alone as I didn't want to invest lots of time and/or money to fix it. Playing Netflix or DVD's looks great!
As for the sound, you are correct that no sound will come over the HDMI especially since it is really DVI to HDMI. DVI is not typically wired for sound. Only some video card makers do that and then you have to use their specific DVI to HDMI dongle.
Let us know how your efforts go.