Alex
From what I've seen, few new stairways are built with the attention to detail you've outlined. Housed stringers, slotted risers,-forget about it. You have built a craftsman staircase and should be congratulated.

Just wanted to let everyone know that my installation of hardwood steps using hdwd flooring is going very well. I have finished 7 open steps and cut off the existing nosing of the 9 remaining closed treads. I used 3-1/2" nosing that I stained and varnished myself. For the risers, I used 1/2" oak plywood, painted white. I used polyurethane glue under each board and wood glue in each joint.
One thing I did differently than is shown in the instructions on this site for using flooring for treads: I put a slip tongue in the nosing on each stair. That allowed me to blind nail the first two rows of flooring ( I ended up with the nosing and three full rows of flooring strips and one half row), then the last row and half row are glued only. If any of these last boards did not fit tight, I drove shims behind them until the glue dried. Also, because of the slip tongue, I was able to use the flooring stapler on the nosing which, along with the glue, is going to ensure the nosings stay rock solid on the treads and risers.
I also found that, when cutting off the existing tread nosing, that a whack on the chisel straight down at each end of the cut would cause the strip of wood to break clean off with very little touch-up.
Just wanted to share these few comments.
And now...one question.
Where can I buy just the oak filler plugs that go on the posts at the end of the rails (I guess there is a bolt behind the plug). I need 4 or 5. I've seen them at the home improvement store, but they come in a package with hardware.
Could I cut plugs from flooring strips using a hole saw?
Thanks.