I have owned my XBox 360 ever since it first came out, but I have just recently gotten into the XBox Live craze. I've had XBox live for about 5 months now, and I just want to say that it is worth every penny I have spent on it. Some might think that $50.00 a year for a membership card is expensive, but for the amazing features and downloadable content you can receive, it is well worth it. I think XBox Live is much better than what PS3 online has to offer.
The only downsides to XBox live are that if you do not have router close to your 360 for your connection, then you have to go out and spend $100 on a Wireless Network Adapter for the 360. Either that, or you can bridge your LAN connection to your wireless connection on your laptop and plug it into your 360, which is a little more complicated, though. The other downside is that in order to get some of the downloadable content, you have to buy microsoft points and spend them. Although, $20 for a 1, 600 Microsoft Points card isn't a bad price for all of the content you can download.
Overall, I would rate XBox Live a 5 out of 5.