For whoever is wondering, I'm using ATI/AMD Catalyst 11.2 drivers with an ATI Radeon HD3850 and the slowdown for the maws is much less than when I used anything from 9.5 to 11.1

Prior to switching to Catalyst 11.2 I got fairly decent results with Catalyst 9.4 drivers. Give it a shot if you have an ATI/AMD card.