I've tried a couple 'medical' soda products here in CA and they were not so much. and man, you think hops are expensive? even with the new laws I suspect prices will stay more or less the same so 1.50/oz v. 300/oz? I'm not experimenting anytime soon and technically it's been a 'legal combination' for me for years now.
Given that many of the active compounds in MJ need to be dehydrated to have a psycoactive effect I suspect that putting it in beer would be a non-starter. but I could be wrong.