cayenne - I read over your other thread, too - so I'll respond to a couple of things.
First, to your question here: yes, I tend to underexpose (according to the camera's meter) when using Marvel. Actually, I rarely even refer to the in-camera meter. Rather, I use the histogram to set my exposure. As Axilrod suggests in the other thread, it is often desirable to preserve the highlights. The only way you can do this is to use the histogram. Also, the histogram I use is Magic Lantern's, which has a very helpful clipping indicator and a way to set/change white balance (and a vectorscope, if you prefer to set white balance by looking at the vectorscope).
Second, I prefer Marvel as a "flat" style compared to Techinicolo Cinestyle in many circumstances because it isn't so flat that you must do a ton of work in post to get some contrast back. However, Marvel is flat enough to preserve some shadow detail and some highlight detail in my experience. Properly exposed (as you are seeing), Marvel looks pretty good out of the camera, yet holds up nicely in grading.
Regarding the lack of LUT for Cinestyle: I never used a LUT and was pretty happy with what I could get Cinestyle to achieve. The problem is that I HAD to apply something to every clip and I sometimes suffered problems with banding because I was stretching so much. My point is that, without a LUT, you get most of the way there by adding back a lot of contrast with either a contrast adjustment or by using curves and adding an S-like shape to the curve. Then, tweak to taste.