I had a similar mounting problem with two drives I had taken from other machines, turned out that their jumpers were still set to slave, not master or cable select. I don't think that caused any problems ejecting though. If it's a drive and enclosure you put together yourself, it's worth checking the jumper settings.
From what I understand, FireWire is better at sustained transfers of large audio and video files, not much difference if you're just doing smaller stuff like Office documents or MP3 files.
cpjakes