CPU Speed vs. Battery

Newer CPUs are much more efficient so even though they are faster, they also provide better battery life. C2D to Sandy Bridge won't bring huge battery life improvements but at least the battery life should not be decreased.

i doubt the cpu change will increase battery life. Maybe when the cpu is like 95%+ idle you might be able to get a slightly better battery life. But as soon as you but the cpu under some load id expect the battery life to be less. For example my friends 2.66 C2D 15" MBP 2009 under full CPU usage had 15 minutes more battery life than my 2.66 i7 15" MBP 2010 which has a bigger battery (400mAh more). So under load the new chips seem to be using a fair amount more power then the C2D's
I definitely realised though that my 15" MBP uses far more power as soon as the CPU is less then 90% idle. Like no kidding my battery life dropped to 3.5 hours when i was utilizing 12% of my CPU. my friends when using 15% was around 4.5 hours.

well a buddy of mine who has the 2.4 i5 15" MBP 2010 gets a bit better battery life, somewhere around 20mins more at a CPU load of 25%. these are the first gen ix processors, dont know how it is with SB.

Well, there's no such thing as a free lunch, and it also applies to CPU speed and battery life. The Sony Vaio i7's have pitiful battery life of 3 hours. The new Lenovo x220's with i7 have 8 hours, but with a 9-cell battery. There's probably some gains in efficiency with Sandy Bridge Turbo Boost, but it's having issues on Dell, HP, and Lenovo platforms right now.