That's of course a real hot button issue and it came up at our MLS this year.
I came up with a compromise using IDX that seemed to satisfy both sides.
We use FlexMLS from FBS and they provide an basic IDX search for every member. It's set up automatically and based on the URL that you normally place on your own website.
We already had an iframe with a rotating "Featured REALTOR" that changes when you refresh the page so we had FBS set it up so that as the REALTOR changes, you also get the IDX search for that REALTOR as well.
All the same rules apply so you don't see the listing office unless it's the one for that REALTOR. Also, if the REALTOR has a website, the link is right on top.
Keep in mind that this isn't fancy but it's the first version, it works, and the buyers agents are happy:
http://poconorealtors.com/index.php?option=com_wrapper&view=wrapper&Itemid=85
Malcolm Waring, REALTORĀ®, e-PRO (also 2010 MLS Committee Chair elect)
Pocono Real Estate