I have a couple maxtor 140 GB drives with dual interfaces, as well as an Iomega HDD 40 GB USB 2.0 drive. I love the portability and have never had any issues with reliability that I haven't seen on a comparable internal.
These days, most of the drives are sourced from the same few vendors anyhow, so there aren't huge differences in quality or price. Pick a fairly known brand and you're good to go.
Just my 2 cents.
