Date range - no problem. The replies might be more problematic, as this is a sense-based engine and the entire article with replies gets shrunk down to 150 bytes or so (that's what makes it so stinking fast). Although, if John feels like integrating, I could extend it to do searches like "where did member X post about subject Y?"
I've often thought it would be useful to see a comprehensive listing of posts between members X and X1 (e.g. is this the freeper who told me to get lost a few months ago?). ;O)