Hi!,
I'm working with a multiselect list that has a lot of items on it and users were complaining about
having to read all every time. So, to solve this I implemented a "sort by user history- list".
Even thought is really nothing that new, the concept seems to be helpful. Here is how:

1. On the DB a view is created in such a way that counts the number of each item by user.

SELECT User_id as ID, COUNT(ISNULL([multi-select values Column ], 0)) AS count
FROM Table
GROUP BY [multi-select values Column ]
ORDER BY ID, count DESC

2. Follow this thread to make it link to the DB
http://www.sugarcrm.com/forums/showthread.php?t=30712

It brought a lot of user satisfaction, although it probably has much room for improvement.

Thanks!