• How quickly does it update normally?  what about if I upload a big batch of text information?  \
• Can it index external files? 
• How much metadata is there automatically and how much can I add?  What about synonyms
• Does it support Boolean operators, and/or the internet operators like quotes and minus signs?
• What is the (general) relevance algorithm, is it tf:idf or something else?
• Are there ways to adjust relevance rankings?
• Are there Best Bets or spelling suggestions features? 
• What kind of search engine result layout tools are there?  Can I get it as XML?
• Are there raw search logs available?  What about search-specific reporting, and integration with other reports?
• What do you guarantee for server uptime and responsiveness?  What if I suddenly have a thousand searches a minute?  a second?  What if someone else does, how will it affect my search times?

I realize this is a lot to ask, but offering search is a fairly bold step, and my readers would very much like to know the answers.

Thanks!

Avi