I've got a Centro. I'm very happy with the Voice Memo feature. From any application, you press & hold the side button, wait momentarily for the beep, speak, and then release the button to stop recording. If you are already in the Voice Memo app, you press & release the side button to record and then a second press to stop. Simple.
I think the Treo 7xxP's work the same way. Don't know about the Windows Mobile version, however.