I just had a tough time deploy FAST Search Server 2010 Beta on a new SharePoint 2010 farm. Upon searching the internet it looked like I had the same issue as loads of other people, a not complete/wrong installation guide. But even after reviewing the posts in this thread and reading the post from Manfred Berry, I was unsuccessful in getting FAST to work.
Until I dove into the logs on the FAST server, which is something I always postpone due to the overload of information in there. I found an error mentioning “Unrecognized attribute ‘allowInsecureTransport’”, caused by the dreaded WCF issue that needs the same hotfix as metioned here. So not only install the hotfix on your SharePoint servers but also on your FAST servers, which seems kind of logical now I think of that.