And that seems to be about it! My old router died recently so I bought an Airport Extreme to replace it. Had I known how little user configuration is possible I'd have bought something else! There is very little control over anything.
I use satellite internet and when my children visit me I want to limit everything, not just the access time, as they'll use my 30Gb monthly allowance in no time if I can't restrict the amount of data downloaded daily or access to certain websites on the guest account.