Hey, I wrote one of these, too! Mine generates and solves all possible puzzles (with my dictionary, there are 54733) in about 1.8 seconds on my six-year-old laptop, and can also typeset them to LaTeX+TikZ to make printable puzzle sheets. That’s 0.03 milliseconds per puzzle. It turns out that you can get this thing to run quite fast once you realize that you can pack words into bitsets and express the whole algorithm…
Very nice! I also took a bitwise approach and ended up with something that solved all possible puzzles in 5 seconds (in 60 lines of matlab).
A technique I used that helped bring the time down was to calculate the points for a given puzzle irregardless of the center letter. This provides an upper bound for the points that could come from that puzzle. After you've done that for all the boards, you sort by upper bound and then start calculating the actual scores for the different center letter options. Doing this for the 538 puzzle, I only had to look at center letters for the top 2 puzzles 'aeginrt' and 'adeinrt' (after those you find a score that is greater than the upper bound for any of the other puzzles).