Re: Jira is the single source of suckage
I am a Red Hat user both at work and personally, and have been for many, many years. I have many years of experience with Bugzilla and JIRA. I have been through a few Bugzilla-to-JIRA transitions. I can only regard them as complete madness.
The "suckage" link above is good, but it's mostly about UI/UX (not only). JIRA was apparently created by people who don't understand SW development and failed - or never took - data structures at college. The most important (the only really important?) relationship between tickets is what blocks what - that determines a partial order. The appropriate data structure is a tree (or, more generally, a lattice). Bugzilla, with a simple plugin, allows one to view the dependencies graphically, as a tree, which is immensely useful. JIRA diesn't - I've been looking for years for the feature since it is so useful.
Bugzilla search and filtering is a lot saner, too. Usually no quasi-SQL queries are involved (not a big problem for me, but too often I've seen managers ask developers to create and save useful JIRA queries).
As the above link mentions there is no real difference between tasks, bugs, stories, etc. They are all things you need to do. The workflow is exactly the same. They can't really be treated differently by anyone. Inexperienced product managers often decide to make features to be developed "tasks" and bugs to be fixed - "bugs". They can't avoid mixing them, however. E.g., one can't prioritize them separately: for each new release there is a bunch of features and a bunch of fixes that customers are waiting for that will consume the same (human) "resources". If any need to be deferred or discarded - which?
And it what may be the biggest (or at least most annoying) workflow problem of all (if it was mentioned in the UI/UX link I missed it): both Bugzilla and JIRA notify you of changes/comments/etc. by email. So you get an email and see someone's comment - what do you do? With Bugzilla you can just reply to the rmail you've just got, keeping the necessary context, and your response will appear as a comment in the ticket. If you send a mail to someone or a group of people, even customers, that is related to a ticket you can just Bcc Bugzilla and add the ticket number in the subject you mail will appear as a comment, etc.
With JIRA you need to switch the interface (between mail and web), possibly more than once, just to react to a comment. In my case, since I work mostly on Linux (yes, mostly Red Hat), but for reasons of "organizational compatibility" (compatibility done backwards, of course) I do mail and some other administrative tasks on a Windows VM I need to switch VMs, virtual desktops, etc. Terrible waste. To be fair, you can email JIRA and make some garbage appear as a comment, but it will be malformed garbage. I have tried using JIRA's markdown to improve formatting - it didn't work.
In short, while it is possible that Red Hat can make it work with a tonne of customizations, etc., I think they are still mad to make this move. Or maybe just not forceful or effective enough to LART some sense into their IBM-minded bosses. Disclaimer: I am a former IBMer as well, and I did run undeclared team/department git and Bugzilla servers there. Well, before JIRA was a thing you could use. Besides, maybe it was just easier in Research.