New contribute features in CS5?

I have CS4 version of DW and contribute and my client is using CS5.  They've asked me to add a new web application to update basic product information, and they want to use contribute.  Can I build in CS 4 and have everything work ok when moved to the production CS5 environment?  Are there a lot of new

features in CS5 contribute that I will not have access to that will cause my clients to be frustrated with the solution I deliver?  Please advise.

THANKS!