To all you 29er's out there!

Okay, currently massively conflicted: the Mary has arrived, but seriously unsure whether the 16" (585mm effective top tube) is big enough. I'm 5' 9" dead on, 32" inseam, longish arms... Should i have gone for the 18"??

Sounds like you're inbetween sizes, i'm 5"10 and the 18" frame is just small enough for me. I was considering switching it for a 16" but then my seatpost wouldn't be long enough so I stuck with it. Sounds like the 16" is your best bet.