The new building is. You can take a (not sure what it's called) moving sidewalk, kinda like the ones at airports, to get there from the original building. On the way there, you get to see the gift shop, which is enormous. Makes you feel like it's more important than the galleries.
I'm making the place sound pretty bad, so you're better off checking out the website at
http://www.nga.gov/ and try to judge for yourself. You may find something you absolutely love which will make the visit worthwhile. I was quickly disappointed by all the closed areas in the original building and may have viewed the museum in a bad mood. It was poorly setup during my visit, your experience may be much better.
Have you been to the Metropolitan, now that's a place to spend a couple of days!