There's certainly merit to the idea as it solves reason #2 in my previous post. It makes it somewhat harder however when wanting to edit the query, I would have to:

a) parse the WHERE clause
b) rebuild the web form
c) accept user input
d) rebuild the WHERE clause
e) rerun the query

Following Occam's Razor logic, if I store it in pure boolean form, I save step a) which in my mind is always a royal pain (maybe because I'm no better at writing parsers than at designing an "expression data model" - sigh).

But thanks for the suggestion, I'll certainly consider it if I come to an absolute stop with my current efforts.