Installed Firefox 1.5 late in the week, and found that external links (like when you click on a link in email) default to opening in a new tab, whereas before they would open in the most recent window or tab. Usually, I’d have to use precognition techniques to know this was going to happen. Thus, I’d either open a new blank window, or tab, and THEN click on the external link.
When compiling in Flex Builder 2, she opens up the most recent HTML & SWF in your most recent Firefox tab or browser window, same as external links. With 1.5, however, it opens in a new tab. A really subtle addition to the new Firefox that really helps when developing in Flex Builder 2.
Now, I can actually keep the documentation open in one Firefox tab while I play in Flex Builder 2.