I used FogBugz for almost a decade until the most complex projects I was working on dragged me into JIRA. I miss FogBugz' email first interface.
My Current stack is JIRA/Confluence on demand, the integration in the WIKI is simply too good to overlook. For product roadmapping I use Aha.io integrated into JIRA.. it's so far a more capable product than JIRA Portfolio, JIRA portfolio doesn't go high level enough. Harvest in the mix for easy time tracking.
The investment of time in integrating projects between Aha and JIRA so far has been a big payoff. We can literally start noodling with ideas high level, and as soon as those ideas cross the line into an epic, we have the sprint ready to go and automatically created in JIRA.
While it wasn't as smooth, the incredible detail we can manage things that need it, while leaving other simple items to hop through the steps that aren't needed was invaluable.
I can see the appeal of that. That is a killer feature for me. My team currently runs what I find to be a pretty lean and clean workflow using Trello, Github (for source control and issues), and Wikimedia for documentation. (Oh, and can't forget Outlook for release scheduling.) Having all of that in one place would make life easier.
On the other hand, not having a monolithic service handling everything has forced us to pay attention to our workflows and practices and keep them sharp.
But the team is small. If we grew or had to manage more projects across multiple teams, this would be really valuable.