In fact, provided the switch is fast enough, even 10 mbps would almost be adequate to play DVDs - the maximum bit rate is 10.08 mbps and many are nowhere near that fast.
It is important to note the difference between a 'star' network (with a switch at the core) and a 'bus' network, such as a wireless one. With a switch you can run at the max bit rate in both directions down every cable at the same time. With a wireless system only one station can transmit at a time and, if you don't use 'ad hoc' mode, each packet is transmitted twice before it reaches its destination. So for the same throughput as a 5-port 100 mbps wired switch you'd need a wireless system running at 2000 mbps.
Yep, if I were starting to build a home-LAN with a view to piping AV around the house, I would probably put a gigabit switch at the core.
Some more info in this related thread:
http://www.cableforum.co.uk/board/sh...d.php?p=199326