Go for Guice if you just want DI. You won't regret it. But always remember, all "auto" stuff might mislead you. For example, you need somebody to start things for you, so in Spring, the Servlet container will invoke the Spring Servlet, which will take things up from there. That's the catch, it's not magic, right? So with Guice, you need to figure out who will so that "auto" for you. Btw, if you're just building a small library, Guice is definitely the DI choice. HTH.
Trying to help find, attend and share what is exciting lately. The sources are completely open :-) I have facilitated private events and closed groups to share comments and photos. I did this because I believe proper socializing happens in real world and the place you socialize matters a lot.
So far we've had a bumpy ride but I am commited to make it work to build a rather truly social planet!
Recommended reading: "Rework" by Jason Fried and
David Heinemeier Hansson, and "Getting Real". Both by 37 signals-the ruby on rails guys. Best of luck!:) trust me, they are well worth the buy...