Yeah, I've gone back and forth on the UTC thing. Maybe if I lived closer to Greenwich I'd be into it, but the problem where I live is that with a 7-8 hour difference I get date changes as a result, which can be a mess. And I'm often going over a time zone boundary in the course of a relatively short interval between shots. So I still have to deal with that, since people viewing many of the photos I shoot expect them to sort with theirs, so that all the dinner and sunset shots are reasonably together, etc.
The other complication is that some software will use (and sometimes insert) local time as determined by the computer the software is running on, and that can go into some time namespaces in metadata. Some time is recorded with time zone, some isn't. So be careful.
Finally, if you're using a camera or sometimes wifi equipped cameras and have the feature to set camera time by GPS then when you flick it on everything changes except the shots you already took. So remember to leave that feature off (if you can, and don't ask me how I know about it...doh!).
Now that I have wifi equipped cameras I've gone back to local time; just makes post work easier since that seems to be the assumption for what's recorded in the image. Plus adding local time is adding the info about what time zone you're in; when I used UTC if I didn't have location info I'd have to infer the zone to get local time. If we got something that could automatically detect time zone we'd be better off in that regard, but for now you need to enter it or record it in some way (a smartphone shot, as suggested, since they are better at getting the zone, at least in populated areas with reception).