I have two publications on a database. One is a transactional publication, the other is a snapshot publication. We have a stand-alone Distributor (separate from the publisher) and both publications have push subscriptions (to the same database on the Subscribers). There are two subscribers (our client is transitioning from SQL Server 2005 to SQL Server 2008 R2, so we're pushing the data to both machines currently). The Publisher and Distributor are both running SQL Server 2005.
I'm using the same Distribution Agent Profile for both publications. When the snapshot is applied at the subscriber, the snapshot publication will honor the MaxBCP setting and push multiple BCP files simultaneously. Unfortunately, the Transactional publication (which is configured to use the same profile for the Distribution Agent) will only push the BCP files serially.
We have a pretty fast link between our site and the subscriber (on the other side of the country), but the single streams only utilize about 2-2.5 Mbit. Utilizing multiple BCP would allow us to take full advantage of the bandwidth. We tested setting MaxBCP to 16 with the snapshot publication and that actually allowed us to burst up to 35 Mbit with an average rate of about 29Mbit.
We're planning on migrating the database to SQL Server 2008 R2 on our side as well and we'd like to take full advantage of the available bandwidth when we reinitialize it on SQL 2008 R2 as the DB is very large (~250 GB).