2.6 Kernel and Centrino

I have a Acer T290 laptop (Centrino) and am seeking to get the laptop to get battery life near what I had under XP. Has there been any recent experience with 2.6.4 and power management?? Is it still to buggy for 9.0?? AND most importantly, is there a simple thread available detailing how you can install the 2.6.4 and keep 2.4 in case you don't like it or it does not work? Thhanks in advance. dse