There is only one reason that I am still using Lightroom and that is the ability to use some external plugins that are extremely useful in my keywording task for thousands of images. I provide videos and stock images and to be able to keyword accurately and quickly is paramount in my workflow.
I really hate hierarchy or structured keywording for a number of reasons that are not the subject altogether. I would like to complete get rid of it in my workflow and would love a preference option to deactivate them.
My approach to keywording is to use a plugin called MyKeyworder. When you use the plugin you type 2 or 3 keyword (lets say Barcelona night skyline) and the plugin suggest immediately dozens of keywords that have been used by other stock contributors to keyword similar files, a few clicks and you have 1 or a batch of files perfectly keyworded in a few seconds. Go to the next one or batch. Now that is an amazing time saver and the biggest reason I stay in LR. If I have to browse, I use Bridge or PhotoMechanic.
If such an useful thing comes ever to PM, I will switch in a heartbeat because I really dislike too many things of LR in the cataloging department, being speed and the hierarchy keywords the biggest culprits. Hope some day something similar appear here.