What do you like best?
Document Management and Search:
The ability to organize many different types of documents, relate them together, search, reuse, and cross reference is very powerful. JAMA is attempting to give you the ability to manage all records (change requests, design docs, bugs, and even test plans) within a single tool. Search is very fast and you have the ability to save and favorite numerous filters.
JAMA fully supports good communication in the form of streams, comments, change requests, and even upstream change notification. If you need to be informed and keep up to date with project changes, JAMA can make this largely hassle free.
We have had very little issue with managing hundreds of users on a single system with a pretty average VM host. With the new docker mode (introduced in 2016) upgrades and management are even easier. You also have the option of a cloud based/hosted solution if you prefer.
What do you dislike?
Though many improvements have been made, there are still a number of general usability issues with reviews (more on that below), filters, and editing. The complete lack of a project wide refactor (search/replace) is just one example of a missing feature that would greatly improve usability. Another example would be per-project pick lists. Large pick lists (over 100) are also not very usable which is why having pick lists per project would improve things a great deal. Another usability issue is dealing with empty values is not consistent in search tools or batch update.
Multi-Project vs Single Project:
It seems as if a misstep was made early on in JAMA development in terms of how things would/should work cross-project. For the most part, you will have the most intuitive experience if you place all related items within one project (sharing a set of versions) but if the project gets too big, JAMA pushing you toward breaking it up because large projects are slow. The problem is, cross project search, navigation, and reporting are limited in some ways and can be confusing for most users.
I feel the review model is simply non-functional. If you are looking for JAMA to implement and enforce good reviews, I would suggest to look elsewhere. Reviews are too complex and review moderators cannot control which changes require re-review so every single change (adding a comma or fixing a spelling mistake) always require 100% re-review from all participants. This is just not workable in my opinion.
What problems are you solving with the product? What benefits have you realized?
Having all the design and test definitions easily searchable and stored in a single application is a huge improvement over a document repository (i.e. file share or SharePoint). Two areas that have shown improvement are better communication and greatly improved document reuse.