For subjects at close distance, the primes can produce nice background blur. The lack of very large aperture lenses is just in keeping with m43 philosophy of small and light. For a similar reason, there are no large aperture longer lenses. But overall, it is a good compromise system. It just needs a few more tweaks of the AF speed and a reasonably priced, high quality 300mm f/2.8.
With the 4/3 to micro 4/3 adaptor.... http://olympuscanada.com/cpg_section/cpg_support_product.asp?id=1328