There are bunch of problems with new released 1.5 version.

Firefox's use of physical and virtual memory is exceptionally high.
CPU usage spikes to 100 percent (usually while loading a Web page).
The browser freezes up for seconds, minutes, or permanently.
The browser won't launch until they remove an errant "firefox.exe" process in Task Manager.
The browser crashes suddenly (usually while loading a Web page).
The browser has trouble loading specific pages, but there's no commonality among users as to which pages won't load.
The initial launch of Firefox loads slower.
Third-party application hyperlinks (such as a link in an e-mail message) take a long time to open a new Firefox tab or to launch the browser

Are you facing the same ?

I have uninstalled it because it was taking lot of time to load into memory.I have 256 RAM but it was very slow to load.