Deleting Attendee(s) / Adding ad-hoc email address
Also, under WM6.x I was able to remove an attendee from a calendar entry. I cannot see any function for this. Highly annoying because if I accidentally pick the wrong contact then I have to start the meeting creation over again. Breaking the meeting creation process into two parts (meeting, then attendee association) is a partial solution but still inefficient. Especially if you are adding a lot of attendees and goof up the last one.
Oh, and not being able to add an ad-hoc email address in the attendee section is irritating. Having to create the address in your contacts/people hub first is annoying and I might not want them in there permanently.