The orange one is a 4 season (why I got it) and it's awesome! My guess is something is not allowing it to fill properly or you may be used to sinking more and maybe need to make it a lil firmer.

As far as hammocks not being warm the Hennessy and other $ hammocks show them being used in Winter, so as long as you have something UNDER you that doesn't allow air to freely move you should be ok.