Working on the setup of the BizTalk deployment we are doing in Dublin right now, I found out that to use the concept of a logical host, with physical server supporting it, you need to have the enterprise edition of BizTalk.
The concept of a stateless host instance is, in my opinion, one of the great strengths of BizTalk and it's a shame Microsoft if only making it available to the ones who can afford the enterprise edition. In Dublin we are deploying a 2 host instance BizTalk group, running on the enterprise edition, so I doesn't directly hurt our deployment now, but it might discourage other from start using BizTalk.