PS - I recommend you read up on HDMI, DVI, etc -
THIS SITE has a decent explanation of the differences. Basically DVI senses whether it is connected to a digital or analog input source and selects either digital or analog output signals - not both. So that is why you can use it with either HDMI (digital) or RGB (analog) devices.
If you want to add digital sound to the HDMI input, you will need a DVI + digital audio interface like the one in the webpage above (pretty expensive IMHO - I'd shop around before buying).
If you are content with analog stereo audio, then you can always run a separate audio connection to the TV (what I do - the TV only has 2 speakers anyway). My Pioneer has separate audio inputs for HDMI inputs 4 & 5, and once set up properly, it'll use both inputs for proper video + audio.
Finally, some HDTVs like my Pioneer have an ethernet port built-in, with DHCP capabilities so I can just connect it to my router and it'll automagically get an IP address. Then I can stream video, pictures, etc from a home server directly to the TV, and don't need to connect the TV to a PC. But I don't think it has a web browser type utility so that you could stream video from an Internet site. Haven't actually tried it yet since I don't have ethernet strung to that location yet.