I suspect the issue may well be to do with how slow one is willing to fly - in this day and age we are taught to fly with such fear of the edge of the performance envelope that most pilots aren't willing to get within a country mile of the low speed end of things. You'd have to be going pretty slow to climb with full flap.
PilotDAR what sort of airspeed are you using for a full flap climb?
Incidentally, I was given to believe (again by a crusty old instructor type) that the reason for the 30degree flap limit on later aircraft was to permit increased MTOW while still allowing the full flap climb requirements to be met.
Practically I've noticed little difference between the 150/152, other than I can't turn final in my customary (very high) position in the 152 without sailing past the numbers at a great height... that last 10degrees makes a big difference.