Thanks. After working through this a couple of times (and cleaning up between each one), I am now getting a "could not convert string to float" error when trying to run the first S/R. This happens even on a smaller selection of books that I know for sure should match up with the regular expression. Time to restore my backup, I guess?
EDIT: Working with it some more, it appears to only match on books where the series name is a single word. For example:
If the screenshot didn't come through:
The title "The Android's Dream (The Android's Dream #1)" does not appear to be recognized by the expression and is unchanged from the "Text Test" to the "Test Result" columns.
The title "Animal Farm (FarmyAnimal, #1)" IS recognized and "Test Result" shows a "1".
Continuing through the rest of the S/R's looks like they are working as planned. Seems to be just the multi-word series giving me problems.