Beyond buying a data integration application, there are a few things customers should keep in mind when thinking about this kind of integration, Berridge told eWEEK.

- Think about what information is actually valuable to your end user, whether it's a sales rep or a manager, and make sure that making a given piece of data available through an integration provides a return that's actually worth the effort.

"Mapping fields from a SAAS to a legacy application can take time, and at the end of the day, the No. 1 piece of advice is integrate only what is going to increase adoption or deliver true productivity improvements on the back end," Berridge said.

To that end, customers should have an idea of how they'll measure improved adoption or productivity.

- Make sure you have a solid strategy in place for guaranteeing data quality. In particular, watch for duplicate records and fields that don't map to the system of record.

- If you want to custom-code your SAAS application, consider using third-party tools rather than an in-house developer. If you rely on a developer, that person may no longer be available in the event of a bug or when there's an upgrade or enhancement.

- Finally, don't overbuild or overengineer your integration. Business people should be allowed to determine the process, and IT should support that process.

That last point was also stressed by David Stover, chief financial officer of Asahi Kasei, a diversified textile manufacturing company with over $10 billion in consolidated sales. His company recently migrated from an SAP ERP system to one from NetSuite.

Stover explained that data has to flow between the new NetSuite system and the company's legacy materials handling application, and said the new hosted application "readily integrates with the complexity we have." The integration process took three months, "half the time of other similar integrations," he said.

If he had it do over, he said, the one thing he would do differently is allow his business users to provide specifications rather than allowing NetSuite to "send their MBAs in there and do a whole business redesign."

Stover recommends having the SAAS vendor demonstrate the new system to business users and have them work with it for a while. "Then come back and see how you can configure it yourself and then get the [NetSuite] redesign people after that."