I just bought a Seagate FreeAgent Desk 1TB, FW800 (x2) for $139 at Frys. It's already formatted for Mac and TimeMachine (10.5) (not that it's a big deal to format a drive...).
It's quieter than some of the older FreeAgent Pro's I have (not sure what model drive either of them use, exactly). Spindle noise is about the same (quiet), but there's an improvement in head seeking noise - it's very quiet. The case design is much more in line with current the Apple line, too - brushed aluminum, white trim, and white LED illumination of the base and logo.
One of the big attractions of this drive is FW800. Most of the time, I find them to be much more expensive [than FW400]. The current FW800 drive I have was built up from bare drive and separate case (Rosewill).
On speed: FW400 beats USB2 by quite a bit, for most tasks. FW800 beats them both. I've measured about a 50% increase in speed using FW800 over 400 (to/from the internal SATA), seeing >60MB/sec (in Activity Monitor).
The only faster interface would be eSATA, but that requires an ExpressCard adapter and doesn't daisy chain. (I have 5 drives and a LightScribe burner on my FW800 chain. btw - when mixing 800 and 400, put the FW800 at the head of the chain)
edit: if you're looking for a bus powered portable, the WD is a good choice. For best speed - get one in a FW800 case (you can get them from OWC, or put one together yourself. I just bought a 2.5" Rosewill FW800 (2x) enclosure from NewEgg for <$50).