It's just a higher resolution, nothing special. Frankly, there is no such thing as HD.
All that matters is that the textures scale properly to higher resolutions, which they do, however.. there is absolutely no anti-aliasing on console games, be it 360 or PS3. I believe some games add a form of anti-aliasing, such as a blur filter or a virtually useless super-sampling filter, but other than that there is nothing.
Seriously, aliasing gets pretty bad on consoles, and it's hard for me, as a PC gamer to not notice it 100% of the time.
When companies show screenshots of games, and they look ultra-smooth and nice, they are either rendered and fake, touched up etc., or they are run through a PC and a powerful GPU with anti-aliasing upwards to 16x or more. Consoles don't even do that, so you'll never see it as smooth as it is on the game box or screenshots they advertise. Some companies get a bit dramatic, others just touch it up a little, some don't bother at all. You can tell the ones that do, though. Remember Operation Flashpoint: Dragon Rising's "uber scene" with the artillery strikes, viewed from a rocky mountaintop miles away? Yeah, that was fake, and rendered.
(Aliasing is Jagged edges on textures, edges, etc., for those that don't know. Hence anti-aliasing, is a render to smooth said jagged edges.)