One misperception about XBL Gold features is that they only apply to people who like to or reguarly play online games.
While a few of my XBL friends with Gold play games online, the vast majority of them are friends in real-life that just enjoy extra company while playing games.
The vast majority of gaming is still a single player experience. This is where the Cross-game Party chat feature really shines.
While I was grinding my way through the final achievements in games like Tales of Vesperia and Magic the Gathering; I would hop into a Party Chat with a couple of friends or seven. All of us are usually playing different games, mostly single player games, but yet we can still just BS about our days, politics, gaming industry, random stuff... We are no longer restricted to just having a solo gaming experience.
This has also lead to each of us purchasing many games we otherwise would not have bothered with. As an example, one of my friends was playing Saints Row 2 while we were talking. He was doing escort missions and just broke out in laughter. Kept telling me about what was going on in the game. The humor really got me interested in SR2 and I ended up buying it.
Likewise several of my friends have seen me playing Magic the Gathering in recent days. They would invite me to a Party Chat and ask me what I thought about the game. All while I was playing the game and they were doing something completely different.
Xbox Live Gold enables whole new levels of community not scene elsewhere, even on the PC (outside of Live Enabled games). It provides a seemless experience across ALL games. Yea, on the PC I can Alt-Tab to get to a chat program, but that breaks the experience. On the 360 I just push the communicate button the 360 chat pad to send and IM and soon a Tweet. On the PC I can setup Skype in the background, but if a game starts hogging resources, the audio will regularly go to hell. On the 360 this is never an issue.
Is XBL worth $50 USD a year? If you have a few friends on XBL that you just to just BS with, have a Netflix subscription and/or play games reguarly online; definately worth every penny.
PSN is definately getting better, but until they get the community and marketplace really up to snuff, it will continue to be viewed as the 2nd rate service. Is it "good enough" for a lot of people, yes, just like Linux and Google Apps are good enough for a lot of people. But like Windows and Office Compete in part by having that extra 20% for each and every user out there that make using the products so much better, so does XBL offer that extra 20% (a different 20% for everyone) that make XBL so much better.
In other words, everyone has a base (80%) usage requirement. Stuff like video marketplace, DLC, downloadable games, online play, friends list, and chat abilities. But everyone also has a few additional features (20%) that they really want above and beyond that. Things like Live Messenger, Twitter, Facebook, Netflix, Last.fm, Party Chat, Cross-game messenging, Cross-game invites, Party invites, Custom Soundtracks in all games, on and on...