Nice straightforward question.

For something over 6 years transactional replication (on sql 2000) was a critical component of disaster recovery for systems scattered around the world that I was responsible for. So I found this one easy, even now 6 years after I ceased to be involved with that (although I have looked to see any changes to transactional replication in new SQL Server releases). But questions about other sorts of replication than transactional would have me scrabbling for the documentation - merge replication seems to me like black magic.