In Mail on iPhone 4, with software update of 4.2.1, it seems my Trash icon has been replaced with "Move to Folder". Is there someway to get it back, so I can trash messages with one keystroke instead of two? I use Gmail IMAP.
It sounds like you might have the Archive button switched on. The latest update assumes you would prefer to archive than to trash.
If this is the case, Go to Settings > Mail, Calendar, etc.. > Gmail Mail Account > deactivate Archive button.