reb large scale slower than 1.8.1

see https://docs.google.com/spreadsheet/ccc?key=0AgLUessE73UXdHRRYnlGaTIyQ0VWa3NWTlVqeDZwRFE#gid=1

reb-in results are not consistent across envs. On terra: 2.0 is slower in terms of medium scale test (reb-1), while slower on larger scale (reb-large-2) tests. But on ec2, results are reversed.