Lightning Network was launched quite a long time ago on Bitcoin testnet. Now, it is available also for mainnet. As someone mentioned earlier, there are about 1000 nodes right now, it's a huge number especially if you take into account that there aren't many services which accept Lightning Network payments. It is probably because it's still experimental feature. A few days ago, lnd released first easy-to-use mainnet client for Lightning Network. I still haven't tested it since I don't have a local copy of a full node.

I have tested Lightning Network when it was only available for the testnet and I was amazed how fast BTC payments can be. You still have to broadcast a transaction when you open and close channel but it is definitely a huge step forward.