As far as I know, as long as the non-runflats are the same size they work fine. I've never heard of having to use rf's with a specific wheel, but then again, I'm no expert. (btw - C5 vette owners usually replace their stock RF's with non-RF's as soon as the RF's run out of rubber)

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.

When I was initally looking at the e90, I asked this question specifically to the stlr, and of course they told me "it was not recommended" which like Nav retofit, means, yeah it can be done, but we wont tell you that...I know several people who have taken RF's off of their Type 162, and put regualr tires on..

Again, its only the "after the fact" situation with RF's I dont care for..I drove for a whole day basically in an e90 with 18" RF, and the ride felt great! Its just the support you get once they die...From anywhere...the service shop, BMW, your wallet, etc....