Very nice. I've been doing some table extraction from PDFs recently. Also check out PDF2JSON for nodejs-based parsing - it grabs all the texts and positions so you don't have to 'intercept' draw calls and dumps them out in JSON.
Of course it has issues extracting data from many tables. There is a body of research literature on how to automatically extract tabular data from PDF (and other sources) and it is not considered an easy task.
You can always fallback to a manual tool like Tabula.
They also have automatic table detection now, but last I check it only worked on certain kinds of tables.
I write the PDF table extraction code for docmunch.com. We think we have figured out how to achieve a very high degree of accuracy in PDF table extraction and how to make a nice UI for manual intervention. We would love to hear about your table extraction use cases.
I've done similar (but more single-use) things to extract text from PDFs, and data from PDF and PostScript plots. PDFs are actually surprisingly easy to dig into when they're decompressed (e.g. with pdftk), since they're mostly text based.