If by Unit Testing you mean... unit testing (testing a unit in isolation), then you actually don't need any particular framework since EJB3.0 are nothing more than annotated POJOs and thus can be relatively easily tested without any special fixture.
Now, if you mean something else - like Integration Testing or Functional Testing - then, yes, tools can help and simplify things (but you should really start to use the right terminology :) I'll assume that this is what you have in mind.
First, JUnitEE seems dead and obsolete and I'm not even sure it has anything for EJB3.x. Second, I'm not impressed by the Java EE 5 support of Cactus and having to deploy Cactus tests is painful (I think that Cactus was nice for J2EE 1.4 but is a bit outdated now). So this leaves us with Ejb3Unit which is in my opinion the best option, especially if you want to run out of container tests i.e. without really deploying the application (much faster).
If you want to run in container tests, then you could indeed use an embedded container and my current preference goes to GlassFish v3, even for Java EE 5 (I may be wrong but I'm pretty disappointed by the starting time of the latest JBoss releases so it isn't getting much of my attention). See the post GlassFish Embedded Reloaded, an appserver in your pocket for sample code (that you could use from your tests) or Using maven plugin for v3 embedded glassfish (if you are using maven).
Another option would be to package and deploy your application with Cargo and then run some tests against the deployed application (with Selenium or a BDD tool for example). This could be useful if you want to run end-to-end tests with a container that doesn't provide any embedded API.
So, to answer your last question, I would indeed use available tools, maybe a combination of them, for tests that are not unit tests and wouldn't mock/inject stuff myself, except if they don't cover some needs that I can't think of right now.