Is it just my imagination or are previously-free plugins switching to a commercial license at a fast rate?
I have spotted a couple because I use them in v4.4.4 and would have to make a purchase before upgrading to JIRA v5.0.x:
JIRA Email This Issue Plugin
JIRA Timesheet Reports and Gadgets Plugin
...but I recall noticing others whilst browsing the plugin exchange.
As it happens, neither plugin that I name is expensive... it'll probably cost more than the price of the licenses just to process the paperwork and even after that I would still consider them good value.