Got a 16gb USB for music. Is it normal for it to add to the boot time?

yes, music from SD or usb take much longer to start that if you had a CD, XM or radio in there.

Is there any way to speed this up? Reformat the stick or something?

well it has to do with the way the avic boots up, the software to play digital music is the last thing to load, and other sources are closer to the half way point, i just recommend not using the SD card for your major source of music, i do not know of any way to speed up the process, but a CD will start playing about half way through the boot up process where a SD card doesn't start until about 1.5-2 minutes later

Im not an ICE expert but i do a lot of work with computers and im assuming the reason that it is taking a while is that the avic checks to see if there is any update data on the card on boot assuming that it is present, it might be worth trying just ejecting the card and seeing if it helps if it does you could just eject and replace every time?

Actually This is with a 16gb USB but the concept must be the same.

this is the beauty of an Ipod, since the avics use the Ipods internal sound processing, playing an Ipod is just a simple audio input and starts playing much much sooner, not to mention you dont have to worry about file folder structure when trying to find and play music.