It's pretty standard. I don't think there are a lot of examples of these stand alone services but Marquee Sports Network which basically is all Cubs, costs that much. At least with Altitude+ you get the Nuggets and Avs.
Hopefully you'll get the ability to start from start or rewind -- Marquee is really shitty about that. You can rewind a little bit if you come in late, but it's glitchy and half the time it shoots you back to live. For $20 a month you should be able to watch any way you want and have a few "DVR" features. Then again, whoever they get to make these apps are likely not in the same league as whoever does the major streaming apps -- and even a lot of those suck on certain platforms. I hope it works well for you guys nearer to Colorado.
Plus Dallas' service is free