CD and MP3 head unit

I figure it's time to jump on this new fangled technology and use MP3 as a source in my car. What do I need to look for and what brands do you like for a head unit? I've had Pioneer for the last few years but had Alpine before in the past and liked it too. I like the option of high power from the deck but it's not gonna be a necessity for this install as I'll use real amplifiers whether it does or not. I will probably still need a CD player as well but maybe not. AM/FM I will need too.
Other options you need to consider are... USB, bluetooth, HD radio, satellite radio, aux audio input (analog), navigation. If you want to store the files on the head unit, you'll have to consider the size of the internal hard drive.

Pioneer makes good head units. Many people complain about their shield ground 'problem'. What they don't realize is that if they have an open shield on their head unit, the internal fuse may have prevented an electrical fire.