Creating Sharepoint workflow with aspx forms in Visual Studio is quite complex.
We don't find many examples, and one of the most important one ("aspxCollectFeedback") provided with the Sharepoint sdk doesn't work.
I've detected 5 main problems in the sdk aspxCollectFeedback example (my version fixes problem 1 to 4):
Problem 1. One project (TaskWorkflowContentType) is not compiled by default.
Problem 2. Gacutil in install.bat
Problem 3.The custom task form doesn’t show up in display mode
Problem 4. “Require Manage Lists permission to start the worklow” option is not used"
Problem 5. The List Content Type case is not handled
check this screencast on my blog
http://sergeluca.spaces.live.com/blog/cns!E8A06D5F2F585013!5717.entry