I think you got it right! The only additions I'd make are:
(a) also index Journal items in addition to Calendar and Task items. Although MS Journal didn't work out as MS originally intended, it's still very useful and would be even more useful if X1 could help find and retrieve information from here.
(b) add user friendly search patterns to the context menu on Outtlook items...things such as "Find all related messages" and "Find all messages to and from you and another person". BTW, the search string for that latter request is...
(to:person_a and from:me) OR (to:me AND from:person_a)
This is a pain to formulate any time I want to search for dialogs between me and another person. Saved searches aren't the answer in this case as most of the time the need for these searches is a one time spontaneoous thing. A built in function that would build this search phrase for me by just right clicking on an e-mail header address and select "Find all messages to/from me and this person" would be most excellent!