Yes, the express checkout process should also send the order receipt... in fact pp_receipt should be only used for express checkout and receipt should be used when they use a credit card on your site directly.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.