Transfer data from partner continuously

I’ve been tasked with implementing a system for continuously receiving large amounts of data from a partner. The data schema on the partners’ side is different from ours, so some transformation has to take place when the data is received and imported into our database.

What’s the best approach for solving this task?

I have some control over both sides of the equation, i.e. if we chose to use WCF, our partner will implement that service. But it’s important to limit the amount of programming that has to take place on the partners’ side as much as possible. Ideally they would use some feature of SQL Server to export their data and then let us deal with the rest.

Other relevant factors:

• SQL Server is used on both sides (2008 at our side, unknown for the partner).
• .NET 4 and/or anything that comes out of the box from Microsoft, no 3rd party products.
• Transfer is one way, i.e. from the partner to us only.
• Amount of data is around tens of thousands of updated records/objects transferred daily.
• The data model is fairly complicated, with several tables and relations.
• The solution should be tolerant to changes on the partner's side (we don’t know when & how they change their model)
• Maintainability and reliability are more important than performance, i.e. we don't need the latest data, but the service should be easy to modify and it can't fail/stop.

I’m asking this question because I overwhelmed but the number of ways this can be accomplished. As a .NET developer, I’m leaning towards implementing WCF or maybe even some custom XML-based exchange. But I know BizTalk would probably fit the bill here, and SQL Server probably has some nifty features built in that I don’t know about.

Any pointers, ideas, and suggestions are most welcome!

In addition to Will's suggestions, you can take a look at SSIS (SQL Server Integration Services). With this you can export to an FTP site and then import it on the other side.