>I know that and I know it is not a bug. I just think it would be VERY nice if the engine could figure it out and optimize it. Or I guess in the help file topic for BETWEEN and EMPTY there could be a note something like "You shouldn't actually use these functions because they stink!"

The help says "ISBLANK() and EMPTY() are not optimizable by Rushmore".
The BETWEEN () function is optimizable as long as the first parameter matches existing index. It's documented in the help also under the same topic Using Rushmore Query Optimization to Speed Data Access