Anyone install Mavericks on a MacBook (late 2009). When I upgraded from SL to Lion it seemed slower but not to bad. Then from Lion to ML seemed to really big down and battery life started to suck. Should I even bother updating to Mav? I was actually think about resetting the whole computer and restoring back to SL. And maybe installing a new battery. But what I have heard in some reports of older MBPs getting better battery life and slightly more responsive. Anyone have any standards MacBook experience?