A friend in Switzerland swears by them, but maybe because ebay / amazon deliveries are not so efficient there.
If you see something on there you want, search ebay and amazon - you might find it there for a bit more, but with a much easier returns process.
I tend to only use Amazon now purely because of the returns - just print a label, take it up the road to the Hermes shop, and refund appears a few days later. No phone calls, complaining emails, no waiting 3 months.