I've experienced similar benefits to what others have posted, since discovering MMM about 3 months ago.
(1) Health benefits. I'm biking frequently and eating (and drinking) at restaurants rarely. I've lost weight because of that, and generally feel more strong and vigorous.
(2) Productivity. I used to assume that most everything that needed doing outside of work should be outsourced. "My time is valuable!" Well, it's not that valuable if I'm spending it laying on the couch watching movies. I'm now getting a lot of things done--home repairs, etc.--and it feels great! I continue to have a long to-do list, and probably always will, but I look forward to tackling the things that are on it!
(3) Peace of mind. This is the biggest non-financial benefit. I have a job that pays pretty well, but is only sometimes (or rarely) pleasant. I assumed I'd be tied to it, or to another similar job in the same field, forever. I'm not qualified for any other lines of work that would still pay my significant student loan bills. But now I've got my spending in order, and understand that just because the term of the loans is 20 years or whatever, I don't actually have to wait 20 years to pay them off. I'm looking to get my loans paid off in a couple of years, at which time I'll have the CHOICE to stay in my job or to leave it. Freedom. Also, similarly, it feels good to actually know what my financial situation is. A year ago, I'm not sure I could have estimated my student loan debt to within $10,000. (Sad but true.) Now I know the principal balance of each loan, the interest rate of each loan, and know all of my other financial information, too. Knowing and caring about the details makes me feel power over the debt, and lets me know that it can be overcome if I continue to put my mind to it. It's a great feeling!
Actually, as I think about it, those non-financial benefits are probably better than the financial benefits. (But because I'm excited about it, I'll still share the financial benefits: I've increased my net worth by $6,000 or $7,000 in just the last couple of months! And there's way more progress to be made as I improve my frugality muscles.)