[This smells like a "which is better" question, but it is not.]
We are using Team Foundation Server 2012 for version control and bug tracking (which is not going to change). We are moving to Agile, and are being asked to use VersionOne to manage the process.
I have attended several Webinars on VersionOne. I cannot get a clear answer on their Team Foundation Server integration story. I cannot find a single significant feature it has that Team Foundation Server 2012 does not have.
What am I missing? Are there better existing integration stories? Does anyone have experience with these two products working together? Does anyone know of any pitfalls?
-- Update --
We've worked with both side-by-side for a while now, and I can share our experiences:
TL,DR: V1 is pretty good for what it is, but it is a silo. All integration is patchwork. You lose almost all of the benefits of integration that TFS offers -- don't get me wrong, TFS has many, many, many, many warts, but being able to link a story to a checkin to a defect to a discussion to a document on your Team Wiki to a specific build is just hilariously better.
-- Update --
We have just started using Coded UI for whitebox testing, and it is stupidly powerful. Having to dupe with VersionOne is just hateful at this point.
If you are using TFS 2012 then I would still question why you think you need another tool to "go agile".
I believe the latest updates to TFS 2012 have improved agile working support so this should still work just fine. You could go for Scrum or Kanban style in terms of your chosen agile working practice.
Some questions that may provoke more thought:
To be honest you could probably "run agile" on just sticky notes if that is what you need.
FYI: http://blog.countersoft.com/2013/03/basics-of-running-agile-projects/