I think I have the same problem of thousand people who can't modify the tx power of this alfa. I'm using bt4.2. Without installing any kind of driver for this device, using the one's installed by default on bt, I'm trying to change the tx power from 8db to a higher level. But it seems to be impossible. The driver that bt loads when i plug in the devices is rt2800usb. With the sudo's rights when I digit iwconfig wlanX txpower 9, bt gives an error like;

Error for wireless request "Set Tx Power" (8B26) :
SET failed on device wlan1 ; Invalid argument.

I tryed to set the crda to BO (iw set reg BO), but the result doesn't change. I've also tryed to modify the script "boost" posted by Jano, changing rtl8187 with rt2800usb but without success. I've read a lot of 3ds without finding a solution. I can agree with the idea of Jano to not extend the txpower to 2W, but now my txpower is very poor.
I think also that if alfa network makes this kind of cards, and many people bought them, it's correct thinking to use all of his power when needed. Otherwise it's a waste of money.

I've also tryed to install compat-wireless-driver but at the end, bt didn't recognize the device at all.

For alfa 36H everything goes well with the default driver.

wishing in a solution...