The primary reason to flash your modem with version 11.126.85.00.209 is stability. I previously experienced frequent "call drops" and the modem overheating after an hour of use. This firmware revision seems to optimize the power management better than the earlier B416 or B418 builds. In a 3-hour continuous usage test, the connection remained stable without the modem getting excessively hot.
This is a 3G-specific firmware. It locks the device primarily to HSPA/UMTS (2100MHz/900MHz). Users attempting to force WCDMA-only modes will find this build very responsive. However, do not expect miracles with signal gain; it is an optimized driver, not a hardware signal booster. -huawei firmware E173 11.126.85.00.209 B427-
Note: If you found this post because you are looking to unlock your modem, please note that firmware updates do not always reset the unlock counter. You typically need a specific 'unlock code' calculated from your IMEI number. The primary reason to flash your modem with version 11