Lee,
I think yours is great, one of the best I have seen, but I think I would make three changes I think when I make one to replace my current one-
* Make a wider base on the back piece that is attached to the table, just to be sure it is totally vertical and more stable (although I admit it is overkill probably).
* You have plenty of adjustment forwards and backwards but I can't see any side to side adjustment. My table will shift slight as it goes up and down so I think I would make the hold-down holes as short slots so I can adjust side-to-side and front-to-back.
* I would also add some sort relief area around the bottom of the hole for sawdust chips that accidently get in there.
Out of operational curiousity- does it do OK with various sizes of blanks? Sometimes when I make slimlines my blanks are only 5/8" but other times they are up to 1" square. Also, after you drill one does the sawdust generated cause any problems? Do you vacumn or just brush it away?
My drill table and fence are very similar to yours, except I used plywood and covered with Formica that I had leftover from another project.