Let's be realistic: if they are giving them away as part of a magazine subscription, it is not going to be a Seiko equivalent, let alone comparable to a Rolex, Omega, Breitling, etc.
My advice is, if you like the magazine in its own right, by all means go ahead and sign up, and think of the watch as a bonus. That way, whatever happens you won't be disappointed; and you might even be pleasantly surprised.