The User Browser administration interface is nice and simple, but when you have 370 users it is sometimes hard to find people.
Allow sorting on the headlines, e.g. sort on Full Name or email
Search on more fields than just email, such as full name and user name
Instead of splitting the result into pages 1, 2, 3, 4 split by characters in the alphabet, e.g. A B C D E. You don't need to go fancy and do A-F, G-I etc, it would be enough just to choose the first letter.
PS The Jira user admin interface is a LOT better than the Confluence admin interface, it's very confusing with the required wildcard characters. Well done Jira!
PPS I guess the "Users Per Page: All" option was designed to avoid the above suggestions