A. It takes longer over USB than AC with the adapter
B. No, it should show up as a removable drive in my computer
C. It's a matter of opinion. WMA has a tad better quality, but drains battery faster than MP3.
D. No, it just may take longer to sync.

Tip- head over to epiZENter.net- practically everything you wanted to know is there. Plus the forums are quite full and more specific to the Zen series.