Very useful for developers, UI could use some work Rated 4 out of 5 stars
Very useful for web development, when you need to test sites with compression off, or with a certain referer, or not accepting XHTML, etc.. It sits there, out of the way, until you need it. It also has an option to have it always on, which could potentially be useful if you wanted to browse with different headers than default.
The UI could use some work. Double click on an item will enable/disable it, and I expected it to edit. You can't drag and drop to change the order, you have to use Move Up and Move Down. Despite these types of shortcomings, there don't seem to be bugs, so it's usable enough.