Let's break it down to what you want to do with your new gadget. The iPad is going to do a lot, but you will find limitations to it, in the way of how fast the network is, when you plan on watching stuff with it.
There are a lot of great minds on here, that can throw out some ideas, and can help you with any technical problems. My wife uses her iPad Retina for streaming, and same with when I use my Nexus 7 tablet. Under the hood, along with the WiFi network, is what will decide how well your streaming will be.
Download the Buddytv app, for controlling your box that you are using, when in the room with your iPad. It will allow you to not only change channels through the guide, but will allow you pretty much full remote capabilities, while you are on the same network, that your DirecTV boxes are on.
I have also used waltzremote.com in Chrome, on both the iPad and the Nexus. It works great for giving you a guide and allowing you to change the channel, with very little overhead, u like the direct app.
I really do not like the DirecTV app, since it is poorly designed, still even at this current generation that it is at.