Although the film hasn't come out yet, the script does seem to carry across Death Note's themes of the nature of justice, corruption through power, etc. The scenarios are also very similar, and really the changes and omissions aren't that significant. Ryuk would look corny on screen (look at the Death Note Live Action) and really serves no significance anyway. Misa would be even more outlandish to a Western audience unless they changed her into a Paris Hilton-esque character, which would get backlash from fans anyway.
Guys, it's not going to be as bad as Dragonball Evolution; at heart, this is still Death Note, re-imagined. If you're judging it already just based on the changed premises and situations, you might as well say Apocalypse Now is a crap adaptation of Heart of Darkness because it takes it all to the Vietnam War.