I enjoyed the structure of this. I liked how we were completely immersed in the lives of these men for the length of the story. It's only about 24 hours of their lives, but they're a momentous few hours.
Yes, I still have questions, but it makes sense given the scope of the story that those answers aren't available. I actually appreciate the HFN ending here, as it actually gives me a lot more hope that Nick and Shane will work out than I would have had if they'd confessed undying love in the midst of all the craziness.