As long as online gaming stays free (not having to worry about me and more importantly my friends to pay extra / subscribe to play together online) and the relatively lag free performance stays as good as is I am just fine with a premium service being offered.
If I would subscribe or not I will look at when the time arrives. Cross-game-party-chat wouldn't be a feature I would pay for, I have my laptop and iPhone if needed (but IMO it's not), text messaging is enough for me (actually even notifications / requests I am not always fond of).
Games like the LittleBigPlanet series better demonstate why I prefer the PSN over XBox Live.