Here's my case:
I'm not an experienced cook (gross understatement), so I'm still very new to preparing my own meals. While it is certainly one of my New Year's resolutions to rectify this, this is probably the biggest obstacle as to why I haven't been doing the Zone.
I believe I've been following a not-100% form of Paleo for most of the work week. I may cheat on weekends or when I'm going out, but my fridge consists of mostly meat, vegetables, nuts and occasional fruit, and I often bring my lunch to work.
I've read the introductory articles on Mike OD's blog and really think that IF might work alright for me, if only because on the surface it seems to justify my current lifestyle habits (which would probably be classfied as unhealthy by other sources). I tend to sleep in, miss breakfast and other meals and wait until after I'm done working out to eat anyway. Then when I do eat, I tend to eat a lot.
However, it's been suggested to me on more than one occasion that I could bring my performance to the next level by becoming more acquainted with my measuring cup and this intrigues me as well.
The problem of course is, as Gant puts it, that one requires me to be quite attentive, at least for the first 2 weeks, while the other requires almost no extra effort on my part (aside from being familiar with my overall caloric consumption).