You need to know more about the dome than the fact that it costs $1200. Give us some more details.
If this is a new dome then it will be able to get all of the Dish programming including HD but it can only get the programming from one satellite at a time. Do you know if this actually is an in-motion antenna? Domes come in 2 flavors, stationary or in-motion and they differ in price and performance.
Is the price you quoted installed or is this a price with you doing the installation work yourself?
Domes work great so don't let the haters confuse you. However, all the dome systems also have limitation compared to an open faced antenna like the Winegard Trav'ler. You just need to make sure the antenna you "think" you want will be able to do the things you want it to do.