Some of the reviews are unforgiving in attacking this flick (CNN, New York Times), although Kenneth Turan gives it a decent write-up at the Los Angeles Times.
I thought it was great. The movie started out as a recruiting film and stars real Navy SEALs. I found myself on the edge of my seat and I could only marvel at the operational realism throughout. Ed Morrissey reviewed the movie when it came out, and he writes:
It’s easy to take this film seriously when it treats its subject with this much respect. Act of Valor celebrates traditional values of duty, honor, and especially sacrifice, and reminds us that every day men like these — and these men — keep us from harm we never knew was coming.
It's worth a look, big time.