Also, am I right to say that the introduction of this new feature means that unlike other cryptocurrencies I would be able to pay for coffee and not to wait until my transaction is completed?
No, it just tells you if a tx with an output belonging to you is in the mempool or not. Previously you had to wait about 2 minutes for it to enter a block to see if it was there or not. It's not instant tx, it's more like "did any of the transactions I saw recently on the network have funds belonging to me". I think it was a Bitcoin core wallet feature from day one.
For Bitcoin and derived forks it's much cheaper from both computational and architectural points of view to check if this tx is mine or not. In CryptoNote wallet and daemon are separated and need additional interfaces to talk about mempool content. And key derivation also consumes CPU.