I use RTM, among other things, to keep track of work tickets assigned to me. Any tasks associated with these work tickets, I tag with the ticket number, which allows for easy searching and grouping. But what would be really handy is if I could do a search where tag:isNumeric or something. I doubt you want to introduce regular expressions to advanced search, but all sorts of other logical operators could be useful. greaterThan/lessThan operators would be great. That way, one could search for a range of things, not just dates.