I use my slingbox pretty regularly for sports, but I can only get 768k upload max from the providers where I live, so the picture isn't that great. Also, my phone has 4GB of data a month then cost $10/GB. I haven't gone over yet, but have come close. Using the bandwith for only live programming, sports, and watching traditional shows via the Nomad capabilities would cut my bandwith use by half.
I have found that the video quality from apps like HBO-GO, Sunday Ticket to-go and MLB look much better than my slingbox due to my upload bandwith at home. I have been thinking about dropping my Directv sports packages (MLB) and using the online version. Between NFL, MLB, NHL, HBO, NBC, TBS/TNT, and hopefully a few more soon, I think I would have plenty of streaming content to chose from. So for me the real question is how do I use my bandwith, and switching to Sprint is not an option for me (coverage). I have an AT&T 4GB Teathering phone plan that I share with my ipad through bluetooth teathering.