Hardwood Floor Nailer
I personally would NOT recommend the manual nailer. I used one several weeks ago, for rather substantial repairs on an oak floor.
It definitely takes some getting used to. It kind of takes the "whole body" and gets pretty aerobic after a while. If you don't hit it just right, you'll send the cleat "most" of the way in--which leaves the onerous task of either trying to get it out--or get it in (I don't know which is worse). To get them (the half-pounded cleats) out, sometimes a claw hammer wouldn't do (the cleats bend easily)--and I'd end up using a vise grip. To get them in--I used a nail set--which sometimes worked; sometimes didn't They'd often bend--meaning I'd either have to break them off or pull them out with the vise grips. Either can be frustrating and time consuming.
The manual nailer is even harder to use near walls.
As if all that's not enough, there are 2 additional reasons I'd shy away from the manual nailer:
1. TENNIS ELBOW! As carpetman suggests, the hammer gets heavy after a few hours. After a lot of use you get worn out and don't strike it using the proper technique. All these things, in my case (and I'm also quite fit--but 170 pounds), added up to a pretty good bout of "tennis elbow." I could barely lift my arm. And of course I kept using it (for other projects)...so the arm hasn't gotten all that much better. Weeks later, it still bothers me. And my wife is so sick of me whining about it, she'll never let me use one again!
2. I've heard it from good authority to stay focused! You have to be careful to have the right stance--OR THE HAMMER CAN GLANCE OFF THE NAILER AND HIT YOUR SHIN. And WOW, is THAT painful. (I, fortunately, never experienced this particular problem.) So be forewarned if you go the manual nailer route.
Or better yet, pay the extra $$$ and rent the air nailer
k2 in CO.
Here is my suggestion of how you should install the floor:
Square up your room. Get your first run installed (take your time and align it right.. the rest of the room depends on the first run), predrill your holes, nail finishing nails in by hand and punch for the first run. Once this run is in place then go get your compressor and nailer this will save you about 2 or 3 hours in preperation work (I find the longest part is setting the straight line on the first edge... and all sides if you are doing boarder work). Now you can run the entire room none stop. To save even more time get another person or two to sort the wood out for the person doing the nailing remember your overlaps, and a little verification that you are not putting some very different colors together (basically orginize the wood for the nailer). They say that you can lay 450sf a day with a phenmatic if you know what you are doing (based on 2.25" wood).
Just my thoughts.