My Z4 with the 18"/sport option has Bridgestone Potenza runflats.

I haven't thought much about them since buying the car. I have had no problems in just under 12,000 km. They stick great once warm. They are a little harsh, but then they are 35 series 18" tires, so my expectations for ride comfort are pretty low. I do know that they take a while to warm up on cool days, particularly when it gets close to freezing (great convertible days...) I have to watch it first thing in the morning.

I figured that with the combination of the RFT plus roadside assistance, I didn't need a repair kit or compressor.

The Z4 boards are full of those who have taken them off for more comfortable tires, or softer compounds, but for general street use I haven't felt the need.

As for special rims, the current generation of runflats use standard rims. I believe that there have been previous generations that used special rims (with a special bead lock to prevent the bead unseating), but not the ones being used by BMW now. Don't know if anyone is still using that design.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue