Blizzard said that activision is forcing battlenet to have some pay to play feature for both SC2 and D3, however they have stated that people will still be able to play for free.
In SC2 it will most likly be some PvP melee match thing with chatroom decoration.
D3 will probably be larger character limate or better connection for payers.
Currently they have not said which features will be pay to use but if they are anything content related blizzard will have major sucerity problems with their worker/managers lives.
As long as I can play my SC2 custom games for free and use everything everyone else can, then I will be happy with the product. With D3 if I can create 8 odd characters and play with everyone else with the same restrictions on level/gear then I do not care, even if payers get an aura or gain levels 10% faster.