1) Nat Geo HD
2) Discovery HD
3) Movies Now HD
The ESPN HD and Star Cricket HD are also real High definition channels. But they are available only for some events like ICC World cup.
The remaining 27 channels are just upscaled ones. You won’t find any difference in quality( may be they are slightly better than Dish TV SD channels due to higher bit rate) . If you compare them to Tata Sky SD channels, they will have same quality. So don’t get fooled by the 30 HD channels news.