It's super useful - e.g. I have an Apple Watch Ultra and frequently take it out without my phone. Having the eSim on it completely changes its utility, especially if I want to do a long ride/run and be confident I can be contacted and/or found when necessary. At the moment I do without the phone primarily for sports activities, but increasingly I find it liberating to leave the phone behind for normal life stuff. With mobile data, the Watch can do most of the stuff I need while avoiding the issues of phone addiction/scrolling. I can do calls, email, messages, navigation, and just don't have access to socials. I'm with One NZ and the marginal additional difference to get the Watch on my contract is well worth it.