People who taut the NFL as a reason to get satellite radio I have to laugh at. Any true NFL fan finds a way to get to a game or sit on his ass on Sundays. I can't see getting it just for the NFL Channel. HOWEVER, baseball is a different story. With a game every day for every team, I could see where baseball on the radio would be a good draw.
The plus for Sirrius though would be the Stern channels. I used to listen to him from way back, so I'm biased obviously, but I haven't heard him much since he got divorced (he got taken off local radio). I've been downloading his show for a month now, and it's amazing. He has two channels on Sirrius, and has other people come in and host shows to the best of my knowledge. Andy Dick did a show, for instance. The satellite format has allowed the show to grow tremendously, about 5 min of commercials per hour, no bleeps.
The best part for fans is that they air their old bits unedited. Also, the shows are much longer, with nearly 5 full hours of content a day. Of course, they are only on four days a week. Fridays they run classic unedited shows, but they still take all the commercial breaks (albeit with less commercials). It really highlights the difference between terrestrial shows and satellite shows.
Final opinion, even though I d/l Stern for free, I would consider getting Sirrius just for all their content plus the Stern channels.