When I had mine done, I mentioned that a colleague of mine had said he fainted. The tattooist said, 'D'ya know, it's only blokes who faint. Never girls. They get themselves so hyped up about being hard about it, that as soon as the needle touches the skin, their entire body floods with adrenaline and bom! down they go.'
Personally, I had mine on my shoulder. It was mildly irritating, and had it not been a tattoo I was getting, I would certainly have sought to stop it, but it wasn't that bad.
However, if you're getting it on your lower back where it's likely to be across the bone, this will hurt. The less fat there is in the area, the more pain.
And as Natalie says, make sure you really want it. I wanted mine (the same design, of my own) for ten years before I actually got it done and don't regret it at all.