Personally I got what felt like a hangover from 2m2b, though it's not the same as ethanol. With ethanol, the hangover is due to toxic levels of acetaldehyde, which is the primary metabolite, which is carcinogenic and really bad for you. However the actually drug effects wear off pretty quickly. With 2m2b, the "hangover", I believe, is simply the lingering effects of the drug. It has a very long half-life so it takes a long time to fully clear your system. So you can get drunk on it, sleep a full night, wake up, and feel groggy/weird for half the next day. This feels like a "hangover", but I think it's actually just that you're still lightly high on it. However, there are no toxic metabolites.
If you take really high doses of it (like 30 or 40mL, that is a VERY high dose), you're going to be igh on it for a LONG time, even multiple days possibly, because it is active in as little as 2mLs. Every half life (~12 hours) reduces the amount of the drug in circulation by about one half, so if you take 40mL of it, after 12 hours you'll still be on 20mL, then after 24 hours, 10mL, then after 36 hours, 5mL, then after 48 hours (2 full days) you will still be on 2.5mL of it, which is still active. Typically, if you are something, you epxect to be feeling normal again after you sleep, so if 2 days ate you're still feeling groggy and shit, it may very well feel like you're having an extended hangover.
I like ethanol quite a bit more than 2m2b... too bad, since ethanol is so toxic (or rather, acetaldehyde is).