Sadly my suspicion was correct... I did a few battery tests, and in fact the carrier hack does decrease battery life.
I tested by leaving the phone in the same spot...
With the hack installed, I experienced battery drain of about 11% per hour streaming music over LTE with the brightness turned up.
Without the hack installed, I experienced battery drain of about 7% per hour streaming music over LTE with the brightness turned up.
It's clear that the hack increases the power output of the phone, thus allowing higher throughput. For many I see it as a positive, but for me I'd rather have the better battery life. The difference in speed is negligible and for those saying "I went from 5mbps to 45mbps, I really question that" ...
I've uninstalled it using the directions on the iTweak page, and I'm back to normal and getting the improved battery life on 18.0 ... hopefully the OP will create something that can increase some of the options that are given with this tweak, without compromising battery life.. but then again that's like saying I want to get more horsepower out of my car without costing fuel efficiency, hehe.