I feel you, I know that I love neurosurgery, but I definitely don't feel like I've adequately ruled out other surgical specialties. At some point you just need to bite the bullet and, like you said, go with your gut because you are going to be working with a limited amount of information no matter what. It definitely does make me a little bitter though that due to the way my school schedules things I'll be going into 4th year not having really been exposed to fields I may have liked.
I know that my interests are neuro>general>ortho. I don't really have a good idea where ENT and Uro fall on the spectrum as I didn't get to experience them this year. On a pure interest level it is going to be below neuro, but how far and is it enough to justify the lifestyle? I agonized over this for a while and then decided f-it, I'm jumping into Neuro head first and if after 2 sub-is (which would put me at August) I feel like I've made a terrible mistake I'll try to either get an ENT application together (I'm competitive numbers wise and it doesn't require away rotations) or worst case scenario take a year off, do ENT rotations next summer and apply then.
Uro is a harder situation. Since it is an early match you really do have to make a choice by early summer at the latest. I'm not sure about Uro, but in neurosurg it seems like doing 1 home sub-i and at least one away sub-i is expected of applicants. You'll also want to have at least one Urology rotation under your belt before applying. I would say if its truly 50-50 go with uro. uro and neurosurg are very very different fields with on average very different lifestyles, acuity of patients, office/OR balance, personalities of practitioners, outcomes etc. If you haven't experienced much of either field try to set up some time over spring break to fill in the gaps (this is what I'm doing with ENT). Good luck!