I can't always get to display the changes that I just made. Sometimes it shows the previous version, particularly if I save first. Then if I make little change, like adding a space, without saving, then clicking on the preview tab will show all of the changes. Then if I save, I get the old version of the web page.
This forces me to constantly upload to my test site in order to reliably view the changes. It appears that when the preview knows there is an unsaved change, it pulls the preview code from the code editor window. When there is no change, it pulls the preview from a cached file that doesn't seem to get updated correctly.

This affects the split screen modes too. You're not always sure what you'll get when you click the refresh button.
(I think there is a similar post on Feb 12, 2007 but no replies)