You can share the data but it can't be done using aliases at this time. The symbolic link method works with soft links. I just tested again to be sure and permissions remained as originally set. I'm not sure how that wasn't working properly in Jayson's case but I'm guessing he's on Mac OS X 10.5.x and assigned another user account read/write access. The additional user permissions will get blown out on a save because CheckBook recreates the file during the save. In our tests we used group permissions instead.
It requires tinkering at the command-line so we won't provide official support for it - but we can still discuss it
. After copying the CheckBook 2 folder to /Users/Shared/ and setting group read/write permissions on it the only command-line work I do is the following:
cd ~/Library/Application\ Support
mv CheckBook\ 2 CheckBook\ 2.old
ln -s /Users/Shared/CheckBook\ 2 CheckBook\ 2
It's also true that multiple users cannot access the same data file at the same time without risking data loss. If you share the data file develop a strong habit of making sure no one else in any other user account has CheckBook running at the same time.
At some point we can phase in some changes to make this easier. The first change would be resolving aliases instead of relying on a file path and preserving permissions when the Accounts file is saved. After that we could look at implementing some IPC to make sure one copy of CheckBook doesn't open the data file when another is already running with the same data file open.