Can't cancel GTB (without spending energy)
Greater Telekinetic blast might not have a valid target, but you can't cancel it
I unlocked GTB and several times, when I tried to use it, the creature I wanted couldn't be targeted (slightly around a corner, but not at an angle that would work). There's no easy way to tell that when you're about to activate the power, and it's not a cheap power.
In addition, if you use the wrong input (I hit space, thinking it was like teleporting rather than firing a missile, and ended up spending my power to do nothing), then you instantly waste your energy even when you didn't intend to cancel. If bad keys just cancelled (and kept the power), it would work out.
Latest steam version (3.1.6?)