I enjoy reviewing Good Article nominations for a number of reasons. First, there's a backlog, so reviewers are always welcome. Second, I learn a lot about a wide variety of topics. And third, I get to know the real workhorses of Wikipedia, the ones are willing to go the full mile to bring articles up to the exacting standards of reviewers like, well, me. I find the criteria, the non-criteria, and the GA templates very helpful. Below are the reviews I have worked on, both finished and unfinished. Promotions that resulted in a Million Award (of any tier) are given the symbol.
In addition, I took over as nominator (not reviewer) for several GA nominations—Tiger shark, United States Declaration of Independence , Bill Clinton , French Sudan, J.D.B. v. North Carolina, and United Nations —after the original nominators dropped out. I finished up the process and made requested changes, and all went on to obtain GA status.
I have also mentored Ammodramus (RCA), Ugog Nizdast (RCA), and Seabuckthorn (RCA) as a GA reviewers.