The following statement is for online play only. I am ignoring any single player games/modes/etc.

Pretty simple. If you want to play Halo or Gears of War online, then xbox live is absolutely worth it simply because without it you can't play those games online. The playstation 3 doesn't have any game very similar to Halo, I don't know about gears because I haven't tried too many tps games.
If you want to play online games with your friends and they all have xboxes then xbox live is absolutely worth it because that will be the only way you can play with your friends.

Personally back when I had xbox live I probably spend a couple of hundred hours a year playing Halo 3 over 4 years. So 60$ for the game + $40 a year was worth it for even just Halo 3.

I haven't enjoyed any ps3 competitive multiplayer games enough to play for more then a dozen hours though, so if ps3 was pay to play online, it clearly would not be worth it for me. It all depends on what games you want to play and what system your friends are gaming on.

Clearly PSN is the better value if you prefer the playstation 3 exclusives/multiplatform and you have friends who play on that console. But if not, its obviously a better deal to play the games you want with your friends for $40 a year than to play something you don't enjoy as much without your friends for free.

You have to take into account some other factors too.

1. Xbox 360's have lower latency controllers and higher framerates in most comparable games (I.E. multiplatforms). So even if the network experience is identical people will still feel that the Xbox Live connection is 'better'. Also the other most compared game, Halo 3 had 100ms latency vs 188 IIRC for the PS3 Killzone 2.

2. The Xbox 360 has skill ranking/comparison in play in all games so you're more likely to be put in with people at your skill level and therefore have a fun game instead of getting your arse handed to you.

3. The Xbox 360 OS makes it easier to play with friends and keep playing with them by setting up parties etc.

4. PSN wasn't really considered 'good enough' until about 2008 going by the consensus here. So if you wanted a good experience you had to wait a couple of years on the PS3 whereas the Xbox 360 had it out of the box.

5. No matter what people say about it in online forums not only could they get away with charging for Live, they could even increase the price! If it was so unjustifiable and terrible for the majority of people then they would not have had the balls to do that.

6. Xbox Live gives the opportunity for subsidised consoles. People seem to compare only the sticker price of consoles when in reality the situation is completely different when you buy the console. The price of a PS3 vs Xbox 360 isn't $249 vs $269 in the U.S. You have to add a $40 controller and a couple of games which makes the price closer to $500 U.S.D. If you can buy the 360 in the holidays for only $100 down with two games you can easily leave the store with four games and two controllers for say $260 which gives you IIRC Forza, Skyrim, Halo and Call of Duty with Xbox Live and two controllers for multiplayer.

I never owned an Xbox 360, but some of my friends do. I have to admit I agree with your opinion, the OS is very quick and smooth, it lets you do many things not possible on PS3 like playing music on the hard drive in any game and chat to your friends no matter what you are doing. It has many indie game unavailable elsewhere. It's very good stuff. PSN is slowly getting there but for now I feel Microsoft has perfected the online experience, even though it costs £40 a year. As for games, there is only so many exclusives i would care about on there, and thats probably Halo. On PS3, there are many more exclusive titles I like, uncharted, killzone, heavy rain, little big planet and others

I probably wouldn't pay more then $30 a year for Live if it wasn't for Halo or Gears (put in over 2000+ hours between both, probably more) just saying.

Though the price is still overstated. I have yet to pay more then $35 a year for Live till this year where I gave up trying to snag the few eBay deals. Ended up paying $40 for Live thru NewEgg.