Yesterday Ulf Wendel created great blog post with deep analysis of JSON UDF functions which I presented at MySQL Connect at September, 21.
Ulf found few bugs in these functions, I reported them all at bugs.mysql.com. You can find numbers in my comment to his blog post. But he also raised concerns, which can not be considered pure bugs, rather feature requests, or even design especiallities.
A question just came up about how to run multiple developers from a single software install. The objective is to have a single software installation on a shared server and then provide different OS users with the ability to create their own domains. This is not a supported configuration but it is attractive for a development environment.