OK. For those of you who are looking to push a multi datastream feed to pachube (cosm), with the new structure this is the way it works for me:
ex. for three datastreams
sprintf(buff,"0,%d\n1,%d\n2,%d\n",datastream1,datastream2,datastream3);
outcome;
0,datastream1
1,datastream2
2,datsstream3
hope it helps,
MaLi