It would be useful to have more flexibility with segmenting, or using segments in campaigns. For example, you can only choose the positive, not the negative, e.g. filter by "all who subscribed in the last month", but you can't choose neither in-segment, nor in-campaign, to "not" send to those people, or segment those who did "not" subscribe within the last month, therefore it's very difficult to send to the other group if you want to, without creating a brand new list. SO either a "not" drop down and adjustment to the descriptions when creating the segments, or a campaign option to send to all in a list "except" a segment would be very handy