While the standard Liferay SOAP methods sometimes suffice, I usually prefer to build my own web service layer using SB. You get to move the business logic to the server side and bundle calls together rather than trying to invoke separate individual calls using the client tier. It also allows you to expose some functionality (i.e. add logic) that may not be visible through the standard API.
As far as pushing data goes, if you're looking at this like some sort of batch data transfer mechanism, you're going to be sorely disappointed. The overhead involved with invoking all of the web service layer to populate data makes it a poor-performing batch update mechanism.
