Honestly, I don't think they're all that bad. But if people lost their shit over Galactus not being a big dude in a Kirby hat in FF2, I suppose it's only expected that they'll do the same if the Watchmen costumes don't 100% match what's on the page, too. And I guess I shouldn't be surprised by the comics internet looking for things to complain about a movie they'll end up going to see anyway.
And yeah, the success-to-failure ratio for adaptations of Alan Moore comics isn't great, but V for Vendetta proved that it can be done reasonably well, so I'm willing to give Watchmen a fair shake. But hey, I'm a reasonable guy.