I'm thinking that the biggest addition most people will be interested in will be the integration of Open Badges. I'm not sure how I feel about that yet. As with everything else, there's a right way and a wrong way to integrate a badge system with courses/students. The whole idea of getting badges for simple things that you would've done anyway would be the wrong way to go about it. More on that in a future post. The ability to customize this though makes for some interesting possibilities.
For me, the most significant addition to this version of Moodle are the improvements made to the Forms. What I mean by this is that whenever you add a new course, resource or activity the list of options for individual settings has been overwhelming to many users, new users especially. 2.5 has successfully been able to compact those options significantly so that the new or occasionally user won't even notice those things as long as the default settings have been set mindfully by a savvy Moodle Admin. As I wrote in my last post, the ideal LMS will allow new users to integrate the tool quickly while still allowing innovators to customize and tweak until things work exactly as they want.
What this means in terms of Moodle training is that people can excel even faster or learn to use the tool on their own more easily because they're not overwhelmed with options. Having said that, I think in some cases people should just suck it up and learn some of those options because that's what's best for kids.