Firstly, Leica R lenses are indeed much larger and bulkier. But this is because they have different focal lengths including zooms and wide anger and what not. Frankly I think they would be rather inconvenient to use on a m4/3 variant camera. If I were going to use them, I would get primes, since I could imagine there being major annoyance in attempting to zoom with lenses that are anything other then on a tripod...If I were to get some of these lenses I would most likely opt for the 19mm, 35mm Summicron or Summilux and the 80mm Summilux. These are all fast and extremely well made, tried and true, test and sharp.
Also keep in mind a lot of the cheaper lenses in this series were made in Japan to "Leica specifications" which is not the same thing as being "Made in Germany" by Leica...just saying...I'm sure someone will get mad about that.
The real reason I see to buy R lenses and use them on a m4/3 or NEX or whatever is because you believe Leica will release a digital solution for the R lenses (other then an R8/R9 with a DMR which is pretty cool btw if you have never used one def jump at the chance) and you either think all the lenses will increase in value and you can make a profit, or because you plan to use them on there.
If you only want to use a m4/3 or NEX then look at some nice Voigtlander, Ziess or used M mount lenses, they are small light and some are reasonably priced and most will do great on smaller sensors. Theres lots of info online, for example Steve Huff Photo on topics like this.
