A smartphone connected via BlueTooth gives you so many more options that I don't consider it being worth the cost and oftentimes has free alternatives to allow you to listen to whatever it is you want to hear.
Ultimately I think a lot of it is subjective and is very situational depending on what you're into. If you're into music, there are much better apps that are free that you can use to listen to just about anything. If you're into live stuff, of course, there's apps for that too. So ultimately I imagine that there is something out there that presents a lower cost, and will be better, than Sirius.
As for me, I find a sub to Google Play Music serves my needs very well for the vast majority of stuff I listen to. There are pluses and minuses, of course (their selection of Prince songs leaves much to be desired for example) but it does virtually everything Sirius does but better. At the time of this writing, I'm paying $16 a month for their family plan which allows me to share the sub with up to 6 other emails/individuals. So one dollar more means I can enjoy it, and so can my immediate family

.