It's over two dozen weapons + new ammo subtypes + mods + new combat challenges and achievements.
And Bethesda is still pricing it only 6 ?/$ less than add-ons lasting from 6 to 8 hours, with all-new locations, assets, voice-acting, etc. etc. so, to be fairly honest, my judgment doesn't really change? Still, more power (and sales) to you!
EDIT: And of course, since I'm a blind fanboy, I'll probably get it, I just don't like the standard price.