Disclaimer: I have not used the M10.
Having said that, I have used the Edirol R09 and R09HR to record lectures. The results were good in the sense that what I recorded was intelligible, and the recordings helped me review those passages that I found hard to grasp during the lecture. The closer to the sound source, the better. This is way more important than the particular recorder you're getting.
I've been doing educational research for the last couple of years, which involved taping high school students in class, an environment that is usually a lot noisier than your typical lecture hall... In this context, the recorders that were designed for speech did better than the Edirols and my Tascam DR-2d which, btw, has cardioid mics. The results were more intelligible and therefore easier to transcribe. There also seemed to be a bit less background noise, which is remarkable because the decks were placed among the students, next to their textbooks, papers, pens etc. so they were exposed to a lot of noise. One of those speech-optimized recorders was an Olympus DM-450, the other one was also an Olympus, but I don't remember which model.
So if I had to record lectures again (thank god those days are over...), I might look into a dedicated voice recorder. Then again, you'll get decent, usable results with just about any other deck, as well.