Humm, I think you give unfair weight to your opinion by comparing a frame of manga with a frame of animation. They are very different things.
Having said that I do agree that the character designs appear to be a little flat; less interesting. I believe it's quite common in anime and possibly why a lot of people who start with manga end up being unimpressed by animated equivalents. I've seen the promo a few times myself and part of me agrees with that point of view... however, another part sees it as having more potential than draw-backs.
I believe it would be very hard for every frame of animation to cover the depth needed for one frame of manga -- naturally -- you're not expected to stare at the animation frame on its own. This is a pitfall I think people often fall into when comparing the two types.
In the manga all you get to present your story/ideas are the text and the "visual aspects". That's it. If you don't make the visual aspects interesting and deep you'd better have Grade A dialogue or it won't be as enjoyable. The rules totally change when you get more frames, movement and sound. Put simply, anime uses a different "tool set" to manga; to criticise one for not using the tried and tested tools of the other feels unfair to me...
Also, although I think you agree, you can't tell from a promo how well the director, animators and voice actors have used the tools available to them. The flow/pace and subtleties that may only be visible for mere moments could be edited out to make the promo shorter or more snappy. Sound effects, dialogue and voice acting that can alter a scene completely are lost when dubbed over with words from somewhere else.
Basically I'm apprehensive too. I really enjoy MnH (and
snoopy, you have my sincere thanks for making it available to me) -- I just don't want people to write off the anime too soon. If people start watching it always looking for where the styles differ (instead of trying to embrace the differences in the two mediums) they won't enjoy it.
Edit: Ugh, too many distractions... I took so long writing this post, it looks like
Scooterboy made all my points for me
oh well...