I just purchased a 410 from Jef. It's a really nice unit, and like John said, it's able to be powered by the firewire bus. However, this only works if your laptop is 6 pin, not 4 pin. If you have a 4 pin 1394 port, then you will have to have external power. Also, the unit hates NEC 1394 chipsets, which one of my computers has.
Jef told me he powered his unit, via a battery from batteryspace.com and it worked flawlessly.
Here's the link to the battery that he used.
http://www.batteryspace.com/product.asp?0=238&1=287&3=172It's only 30 bucks... so, it's very reasonably priced, for an SLA and charger.
Peace,
Dave