Free moves are good, sort of.

If you're on server A, most people will stay there even if it were free to move to server B.
So, while the service is free... it won't be that big of a benefit for most of us.

I can see it being nice, if you're in a progression guild and want to transfer servers.
There were transfers in Everquest, when a guild was looking for a specific toon to fill their raid roster.
Or if you have friends on another server.
Or even if you want to try PvP or move to PvE so you're not ganked.

It won't be a useless/dead service.
But even if transfers were free in Warcraft, I wouldn't leave my server.