That I know of there have been two previous Hollywood movies that was set among the U.S. Navy Seals. The were Navy Seals made in 1990 and G.I. Jane in 1997. Both of those were extremely unrealistic. The real world special operations military in any nation's military just doesn't work the way those movies imagined. Act of Valor was very realistic.
There were no Hollywood stars or even near stars in the movie. All of the Seals parts were acted by genuine Seals. All of the weapons, systems, and tactics really exist and are really used in the way shown. The movie is modeled on real operations that really took place, with heavy altering to protect classified information.
At the very end the movie shows a list of all Seals that have been killed in action since 9/11/01.
The plot isn't anything special, but it was refreshing to see such realism.