In looking at their page, http://screenshot-program.com/fireshot/ -- it appears to be free, but they would like you update to the professional version, which offers a few more features, which you're not been using (unless the free version came with a trial to the Pro version).

In looking at that page and at the pro version page, I see nothing that you can't do for free with the one I use which is PicPick (picpick.org), which is free for personal use only (non-business use). It is separate from all browsers so does not add overhead to any browser.

You'd probably want to stick with what you are using, unless the annoyances really become bothersome. The transition between such software is very simple, the tools look the same to me, the layout is different.

PicPick is a good free program, but I've decided to use ScreenShot Capture as it appears to be somewhat more robust than PicPick. FireShot was OK, but became too annoying to continually use.

EDIT: Comments made on the Firefox addon site for Fireshot indicate that it is no longer free (https://addons.mozilla.org/en-US/firefox/addon/fireshot/)