Early last month, it was revealed to much outcry that the Transformer Prime had a locked bootloader. Angry customers took to the forums to vent and started a petition to get Asus to change its stance. And just 24 hours later, that's what happened, with Asus promising an unlock tool down the road.
Today Asus delivered, with the unlock tool hitting the TP's support site:
TL;DR: Caveat emptor.
The company strongly suggests customers stay away from unlocking the bootloader, stating:
You also acknowledge ASUS does not guarantee service satisfaction to any Revised Product, including events involving paid service requested by you to be performed to the Revised Product.