1. I like his financial reform plan, his education reform plan, and his criminal justice reform plans. They are all very comprehensive yet workable. (If you want the specifics of these plans, they are on his website and can be found in DU's O'Malley group)
2. I like his youthful enthusiasm, hard work ethic, and problem-solving attitude. This makes him the most electable candidate in my opinion.
3. He is not just talk. He has already accomplished many of his plans/ideas in Maryland and it has paid off. Maryland is a top education state, decriminalized marijuana, eliminated the death penalty, raised taxes on the rich, was an early adopter to marriage equality, and one of the few states that does not allow discrimination against transgender citizens. Add in an ethical approach to immigration and pro-environment views and you have the best candidate, imho.
PS. You disclaimer about not bashing other candidates in the O'Malley group is unnecessary. From our SOP: "The Martin O'Malley group serves as a safe haven to discuss and learn about Governor Martin O'Malley. As fellow Democrats, bashing other Democratic candidates is not acceptable. This is paramount to participation in this group." We have over 2K posts and have avoided bashing our party's other candidates.