It certainly takes some time - most of that time they just leave it installing which is why you aren't having to pay £150+ per hour to get it installed.
Certainly worth it for £80. You get a choice of what Navigation app to use (Apple maps, Google maps, Waze) which are all better than the built in nav with better real-time updates. You can use Spotify, the vehicle will read out text messages (reliability) and a user interface that is easier to use when on the move compared to the Lexus system. You have access to other apps too such as Audiobooks, Audible, Webex if you need to join a conference call etc.
You can still use the Lexus system if you want - and use both, so you can put on the radio and then switch to CarPlay for Navigation for example.