I have the PreCip jacket, which has a breathability rating of 12,000 g/m^2/24hrs. The MemBrain fabric has a breathability rating of 25,000 g/m^2/24hrs. This means that the MemBrain fabric should have greater than twice the breathability than the PreCip. I wear the PreCip jacket over a zip-up fleece sweater in the winter while biking and I have to say that I can literally feel the jacket breathe, allowing some heat to escape so that I stay dry. I know it's not the wind as the jacket is windproof as far as my knowledge is concerned.
If you are wondering about what the g/m^2/24hrs means, I believe it simply means that one square meter of a certain material will allow (for the MemBrain fabric) 25,000 g of water to escape during a time period of 24 hours. I am personally looking at this jacket for the future in case the reviews about the PreCip jacket are correct - that after a couple years the material doesn't provide waterproofing anymore. Overall, although I do not own this jacket, I believe that it will serve as an excellent jacket for any active outdoor activity. The only thing I would look out for personally would be if it crinkles in cold temperatures - if it tends to stiffen up and make a lot of noise while moving in it.