This year's API wishlist surveys are now ready for several Autodesk products, as Kean just pointed out, and will remain open until May 30th, 2010. Here is a direct link to the Revit API wishlist survey.
To quote Kean, it really is worth providing us with your input: it's one of the most direct ways to influence the direction of the Autodesk products you customize or for which you develop applications. Tell us which APIs are most important to you: your feedback will not fall on deaf ears. And if you (optionally) provide your email address in the survey, Kean will send you a copy of the results once they've been compiled. Thank you in advance for your feedback!