That battery has seen some action.
there's a number of factors to consider here - first off, linux really cannot (as of now) fully utilize ACPI/USB/Expresscard/Optical drive and of course, CPU power saving techniques. Combined with Linux's less-than-optimal Power controls, I'd be willing to wager your computer was running warmer too all this while. Heat affects battery life greatly, and even though the firmware may be reporting 227 cycles, I guess the state of the battery may be worse for wear.
Bitlocker's power consumption (or lack thereof) is a debatable topic. From My end, I'm using two SSD units (one for OS, one for Data) and i'm running cooler, quieter and a little bit longer than ever before. Depending on what you do with you computer, bitlocker could
use some power if you use a lot of disk-intensive programs-how much is something nobody has really measured so far. A SSD will definitely make things not only quicker but also save you some battery power and generate less heat.
I would disable Aero and all visual effects, select a dark, plain desktop background to lower power use. you can also look at the WLAN card's settings in Device manager (under the Advanced tab, and reduce Transmit power and roaming aggressiveness, if you sit close to your wireless access point. The Power manager has some options for disabling USB charging (if available), Expresscard Power, reducing brightness during bootup and shutdown, and more. try playing with those and see what you can eke out, but I think a new battery might be required a little down the road.