It seems that if Mail, Address Book, and iCal were merged as one application instead of two separate ones, the applications would be much more useful. Here are a couple of tasks that could be simplified with a merge of the applications: linking a date with an e-mail, inserting address book contacts in Mail (Address Book is small enough, why not just push it into Mail anyway?), linking todo's in Mail with certain dates and see to-do's that are still to-be-done, and the list just goes on. Maybe this doesn't necessarily need to be addressed in Leopard, but it'd be nice to see it in OS X 10.6.
Here are a couple other advantages I didn't mention: less Dock space, less disk space (Address Book, iCal, and Mail obviously have some shared code), more organized. What's your opinion on merging the apps? Is it a good idea, or do you not agree with it?