The answer to the first question is, "very few". The answer to the second question is that full length departures are still available if needed (the remaining runway available from TWYM2 is 10950ft). In fact, 777s and 747s are exempt from this program as well as anyone else with an operational requirement. Furthermore, it will be suspended any time the Takeoff area (TWYP and M2) can't be seen from the Tower or when taxiway congestion requires it to be lifted (when things get busy on 9L they used to use parallel departure lines on TWY M and TWY L. The loss of TWY L could spell gridlock at very busy times.

Apparently during the Planning phase which began in April, the biggest concern came from Jetblast on aircraft crossing at TWYP. I've seen the data for everything up to a 76-400 and graphically the jetblast footprint would not appear to pose a risk, but this is likely the reason for 777/747 exemption. When issuing Takeoff Performance data via ACARs, Delta aircraft will now routinely receive data for TWYM2 departures. The interesting thing will be to see how well the information about this new program is disemminated to airlines who use ATL less frequently because if your Takeoff numbers are for full length and you are offered an intersection departure, even if you intuitively know that you can easily do it, technically you need 'numbers' for the actual takeoff lenght in order to be legal.

While this will certainly save time and perhaps some gas, the biggest benefit from a Pilot/ATC operational standpoint is the reduction in Runway Incursion risk. The planning folks say that this will eliminate 650 runway crossings on a typical day when using eastbound flow. I can tell you that multiple frequency changes, terrible frequnecy congestion and the fact that departures and arrivals were on separate frequencies often resulted in Runway Incursions waiting to happen. Traffic outbound to RWY10 will still have to cross 9L/9R downfield.