What do you like best?
It has everything! Everything you need to build your perfect app is available in the Spring Framework. From Mobile to Security to Data. Spring 4 provides you with "less writing, more doing". I see it as a convention over configuration. You no longer need those nasty XML configuration file, everything can be customized with java code.
Let's not forget Spring-Boot, to easily configure your application and you're ready to go.
The community is huge! You need help with something, you have it!
What do you dislike?
Spring have its limits... If you're picky enough to have a need for a certain feature, you'll need to dig into the source code of Spring to see how it's internally done to understand some concepts.
It's a big framework, so for some situations, big = slow, but it's not that bad. Depends on your needs and how you code.
Recommendations to others considering the product
Spring is, IMHO, the best java framework out there to build a powerful application (web or mobile). I really recommend!
There are a lot of tutorials and examples online. It's easy to learn if you already have a good java background.
You're having a hard time with a certain Spring feature? Look it up on Stackoverflow. Chances are, you're not the first one...
What business problems are you solving with the product? What benefits have you realized?
We're building a new web app and mobile app and Spring helped a lot for configuring everything : Security, Database connection, the RESTful API, smooth integration with Hibernate. schedulers (thread pool tasks). Basicly a complete back end for both a website and an Android and iOS app.