Hey thanks! We spent ALOT of time debugging and optimizing it. Cerv and Kham pretty much put it through the wringer to test the complex logic under horrible spawn conditions. Every time they came up with a "AH HA, your logic doesn't work!" I had to demonstrate it was their rules that were wonky. heh. But it crashes much less than many other looters out there just from the heavy amount of bulletproofing that went into it.
If you look at the guts of the search algorithm, it's very streamlined so that only one event property is performed on each item, and double-linked lists are used for index of properties, so no iteration occurs within each item. It's about as fast as EUO can do. Complex rules were only possible by letting EUO run in its form of "recursion". I ported the search engine to OEUO and the resulting performance was amazing - several seconds compressed into just milliseconds. But it's a good balance of speed and stability. Other people have gotten it to run faster, but they always impact stability.
I've thought from time to time to post this one at EUO just to get a wider audience since it is useful at so many levels.