I have couple bottles of the original, vintage M7, as well as the new M7 Oud Absolu. The vintage M7 wins hands down - I much prefer it to the current release.
The vintage one has a cherry syrup accord, which sounds a bit medicinal and personally I was very afraid of (I *hate* processed cherries in any form, I only like them fresh), but it turns out that the way they blended that in M7 it actually works and is a very very comforting scent. It reminds me of my childhood, and that one time when my grandma took me to a local apothecary for some of her pills and potions. I must have been maybe 5 years old then, but the scent of that place remained engraved in my brain, and the vintage M7 kind of reminds me of all that. Good, fond memories...
The current M7 Oud Absolu does not have the cherry accord at all. They replaced it with patchouli I think, as I detect a whole lot more of it, and practically none in the vintage M7. The difference is most noticeable in the top notes - the vintage starts with a big wow impression, the oud absolu is a sort of semi-boring concoction, kind of sour aoud. In the drydown they get closer in their similarities, however, after having worn the vintage M7 I can safely say I have literally zero interest in using my Oud Absolu bottle ever again - it will likely remain 99% full until I give it away or sell it (PM me if you are interested).
M7 vintage is still (relatively) easy to obtain on eBay, even though the prices approach $200-$250/100ml. I do think the price difference is quite justified though, and even though I still have two nearly full bottles, I would most definitely seek and acquire another vintage M7 if I was running low. Highly recommended, and I think if you are into this hobby you should have a bottle to know what the fuss is all about, or at least a decant from a reputable source (just so you know you are getting the vintage, not the current Oud Absolu which is far different from the original).