I'm one of the people you emailed it to, so thanks for that!
I used applications (both desktop- and web-based) for ages, but 3 batches ago I switched to my own spreadsheet. I use Numbers and sync to all my devices using iCloud, but I'll likely find some tidbits in yours to steal.
Although mine is still a work in progress, I agree with all the sentiment here. I like being fully aware of what formulae I'm using, being able to tweak every constant easily, and most of all, being able to add calculations as needed. For example, the other day I needed to know the mass of the cast-out wort. Adding that to the spreadsheet was trivial, and now it's there for future batches should I ever need it.