If you need mobility, the Edirol FA-101 is a pretty good choice. The unit is made of sturdy aluminum, it's compact and light yet very sturdy; The overall latency is very good, so is sound quality (from both the AD/DA and pres), the driver is solid, has very good S/N ratio, it features direct monitoring and can be switched from buss power to included external PSU. I got mine for $374.00 Canadian, which makes it one of the lowest cost 10in/10out Firewire audio interface on the market. Oh, and it looks very sexy
On the minus side, you can't switch sample rate on the fly like most of the others, there's only one high Z input, the driver is minimalistic at the extreme (entirely devoid of any creature comfort that one usually take for granted), there's no facility to rackmount it and, like most, if not all, interface in this price range, the pres can get a bit noisy if pushed very hard.