<p>I personally am of the opinion that anytime you are in a position to get another degree that doesn't cost you anything in terms of time and money, you should probably take it. Looking at the issue from a high level, In the case of MIT LFM, Northwestern MMM, Michigan TMI, or these other special dual-degree programs, since you're going to be spending 2 years getting your MBA anyway, why not also pick up an accompanying Master's during that time? </p>
<p>Now, on a more detailed level, I agree that things are not quite that simple. In particular, if you have zero intention of working in tech (i.e. if you know that you want to be an investment banker), then I agree that picking up that 2nd degree may not be a wise choice. That 2nd degree will soak up a lot of your spare time. You are probably better off spending that time practicing for your banking interviews. In other words, there are definitely good reasons for some people to prefer regular MIT Sloan over LFM, regular Northwestern Kellogg over MMM, regular Michigan over TMI.</p>
<p>Furthermore, I also agree that if you already have an MS, then the allure of these programs diminishes somewhat. However, not entirely, I've known people with PhD's in engineering who went to LFM. Randal Pinkett, the winner of Donald Trump's Apprentice 4, completed an MSc in Computer Science from Oxford as a Rhodes Scholar and then went to MIT LFM, picking up an MBA and SM in EECS (then stayed at MIT to pick up a PhD from the Media Lab, then started his own company, then wound up as a contestant on the Apprentice). </p>
<p>While I can't speak about TMI or MMM in great detail, I can tell you that one of LFM's great calling cards is that it lets you try to get your engineering SM in any engineering discipline among all the participating LFM disciplines. Currently, I believe all of the eng disciplines except nuclear engineering participate in LFM. Historically, about 1/4 of all LFM students come in already having a master's degree or a PhD in engineering. Many of them see LFM as an opportunity to learn an entirely new field of engineering. As long as you can get decent grades, you can get your SM in whatever engineering you want. For example, one guy already has his MEng in EECS from MIT, and is now in LFM, pursuing his SM in Materials Science, because he's interested in nanotechnology. </p>
<p>By the way, if you're confused about the 'SM' designation, that's what MIT calls its Master of Science. Most schools say MS, but MIT says SM. Just like MIT doesn't hand out BS degrees like most schools do, but rather "SB" degrees. Don't ask why.</p>