Sorry...haven't had the time to compile a documentation for all of the features... hopefully I'll get to it pretty soon.
You don't have to be using Axure to benefit from the Plugin... every so many days (manual setting) it will as you if you want to make a backup of the project (creates a folderstructer where it stores everything).
As far as the Use case editor goes... it has a couple of extra functionalities (compared to the one from EA) that I find very usefull.
For example the steps in a UC are numbered, and the plugin keeps track of these steps... so if you reference a step in some UC and then later change the step order in that UC ... it will automatically update the links so your reference is still valid.
For a future release I'm planning on implementing an automated Activity Diagram generator (since I can programatically sort each step hierarchically...this should be possible)
You can also define rules for a use case... for example every use case needs to have a Note, has to have at least 2 steps, each step needs to have at least 2 words...and so on. Also, depending on the phase that your project is in, you can validate agains different rule sets.
It will identify if selected UC is Extended, Included... and provide default steps based on the type. (I want to get to where a user can specify the default steps...but that's for a later phase

)
If you have multiple projects in one repository... you can't really keep an issues list per project...it's always for the entire repository.
SpearFish allows you to define a Issues List or a Glossary List per project. (Creation of such an item is done through SF and not EA)
I'm still working on a Meeting Report Manager where you can register you meeting minutes and link them automatically to a EA object.
I find it very usefull when you need to know anything that was said about a particullar Screen, Use Case, Requirement...
As you can see it has a few functionalities... and unfortunatly I haven't had any time to document all of them extensively.
Hopefully I'll get to it pretty soon!!