the 21 is excellent Badmonkey. The port is the ideal addition for complexity, always present but never dominating, just in the background balancing with the typical Balvenie honey and vanilla flavors.
Its a sweet malt, well aged without the loss of character although it might seem a litlle mild and soft comparing to the 15 for example. i found it a great whisky with lots of complexity as is so common with port and whisky. Very well balanced too, with the typical honey and well matured oak right inthere with the port.
i tried the 1989 Port wood too but that one wasnt impressive at all, i think its young age was an disadvantage as the port was a bit dominating making the whisky very winey and a bit sharp. the 21 has none of that.