I had quite a few problems with the launcher; getting stuck at updating tools, stuck at launching etc.
I kept trying the proposed fixes such as killing the Agent process in the task manager, deleting the agent folder etc, but none of it worked.
What did fix it for me however was constantly killing the agent process over and over, while keeping the launcher open, i.e. not ever closing it down; I was stuck at updating tools (0%) but every time I killed the agent process it reset and attempted to do it again.
After a few tries it eventually starting getting past 0%, but continued to get stuck. However it eventually it updated all the way, and I was then able to log in and I am now sitting at the character select screen.
So yeah, just keep killing the agent process with the launcher open (not while you are stuck at "launching; you will need to reload the launcher first.)