Formatting hours is a really useful option to me. However, being stuck with the AM/PM formatting is really annoying, especially considering that the 24h format is used in a lot of countries and is even the ISO 8601...
In short I would love to see the option in the formatting... The strangest thing is that it is available when using the date&hour format... Please be consistent and give the user the choice on the formatting they want to use :)