'I'm loving it'

Why is the progressive form used in McDonald's slogan: I'm loving it.

Why? You'll have to ask the advertising team.

This has been discussed a lot on this forum. I'm not sure if the "related threads" links will help, but by giving your thread a good title (thank you!) you have access to them.

It's a myth that you can't use the progressive when situations are temporary or new.

Because it's unusual, it sticks in the memory, and advertising is about that. It's a very effective phrase that has taken on a life of its own.