There are definitely a few things you can do to improve performance. What are your current JVM parameters? We have some recommendataions on these.
<div class="jive-quote">Which features utilize the most system resources etc.? </div>
Read Stats and Status Level calculations are heavy resource users, especially when you have a large amont of active users, and large amounts of data to be kept track of.
Lastly, caching is responsible for performance problems as well. Have you checked out your cache settings from within the admin console?
Check out this video for some further explainations of these topics: http://www.jivesoftware.com/community/blogs/podcasts/2007/10/18/clearspace-performance-tuning