The connection with the supplied external sensor was amazingly fast and without any problems. Since I already had other 433 Mhz sensors of different weather stations, which could be coupled only after minutes or not at all with the main unit.
The only complaint goes to the alarm. That could be somewhat "discreet" and some just go in the first few seconds less aggressively works. Here I would like to see improvement as a slightly longer "swelling" of the alarm tone.