If the customer is ok with it, why would it be an issue. VS2010 Beta2 comes with a GoLive license so you can distribute .Net 4 apps. Also, you can work with VS2010 and target the 3.5 framework.
>3rd if he wants to do any work for a customer, he is not supposed to be using a beta development tool.
Craig Berntson
MCSD, Microsoft .Net MVP, Grape City Community Influencer