I am using a Mac Mini with Mini-DVI to VGA. Looks okay, but I was wondering if I will gain anything if I were to use Mini-DVI to HDMI to the 50" Sony LCD TV? TV can only support up to 1080i.
I have a 56" Sony LCD TV (1080p), and when I hook my MacBook Pro up to it, I actually get a worse picture when I use an HDMI cable. Everything looks great with a DVI->VGA cable, but I see odd artifacts when using a DVI->HDMI cable. I might just have a crappy cable or my TV settings wrong, though.
I think your setup is just fine. You might notice a slight difference if you DL the HD Rentals from the iTunes store with the HDMI, but regular content will look just as good with either setup.