[davem3fan]

My E90 M3 with (32k miles) was in last week for Scheduled Maintenance.
I asked them to do the PS fluid as a good pro-active maintenance measure.

When I picked the car up, the job was done... and I had a chance to chat with the service manager who shared his experience:

He agreed that it is a good idea. In his experience (even in cars that were not neglected) almost all PS fluid he saw was "pretty ugly" or smelled "burnt". For someone who really cares about their car, it is a good peace-of-mind choice.

As it is winter in PA, I've been driving windows UP, but to me turning the steering wheel feels slightly smoother and the pump is quieter in parking maneuvers where you can actually hear it.
I may have been just slightly below capacity on fluid level anyway.

I'm happy I did it. YMMV.