Here's how your customers think you process their enhancement ideas. 
I used to do a simple presentation for customers (and sales people) that illustrated how ideas turn into features. Carl Knibbs suggests this process:
See Carl's post at http://www.carlknibbs.net/blog/2010/2/10/how-we-build-the-product.html
Customers want to know that you have a process for planning and prioritization. Most customers don't really mind being told "no"-- they mind being ignored. So the next time you have a group of customers onsite, think about a simple presentation (and maybe it's a single slide) that shows your planning process. Maybe you should show them your prioritization system and get their feedback. For more on prioritization, see http://pragmaticmarketing.typepad.com/productmarketing/2010/02/setting_prioritites.html
