Agreed. I and several others have been banging away at MT for a while on this - we have permanent users who purchase a monthly datacap, so we only need;
1. a way to reset user's counters to zero at the beginning of each month without losing their month-by-month history. This requires a way of closing all existing sessions and restarting new ones at 0001 hours on the first of the month,
2. a way users can access their own monthly usage to date with a simple button-push instead of complex URLs, user-names and passwords.
MT's hotspot could do this, but MT has concentrated exclusively on the 'Starbucks'-type hotspot when designing theirs.
Some of us have been working on scripts for this, see
http://wiki.mikrotik.com/wiki/AutomatedBilling
which might offer some suggestions.