I had one on my 2003 520. It didn't look sturdy, so I put it on my commuter bike where I rarely used the rack for anything more than holding a jacket.. It broke after a couple months.

I have a Jannd Expedition rack on my 520 now. It has held up well for a two-day tour, weekend 50mile+ rides, and regular commuting while holding one or two Arkel t-42 panniers. In a couple weeks I'll start a 500+ mile tour with it holding two panniers, a trunk rack, and a couple other items strapped to it.