Here's a link to my review of my 2015 M5.
http://www.6post.com/forums/showthread.php?t=1114015
It's definitely a torque monster. Nannies will protect you, but this thing can and will kick your butt with MDM switched on.
Regarding oil consumption, some do and some don't. Trust me, you don't want to start a debate about why that is. See if you can find out the service history of yours and how much oil has been added and how often changed. This may give you some indication, although if the dealer adds oil, it may not be recorded and if the owner added oil then for sure you won't know.
One thing you can do is look at the tail pipes. If they're really black and don't clean easily, there's a history of oil burning there. You didn't mention how many miles are on it.