Congrats to Nalbandian, if he fails before the semis in Australia he will be declared a fat waste of a player and if he happens to win the title he will be declared the undisputed GOAT with the prospect of winning at least 16-18 slams.
However, I still think Djokovic would be a better choice for the year award.
I think Nalbandian deserves bandwagon player of the year. Written off at the beginning of 2007 for being an overweight, under-motivated underachiever, he ended the year in spectacular fashion. One never knows whether he can carry forward his recent form to the AO, hence the bandwagon effect: here today, possibly gone tomorrow. (Having said that, I sincerely hope he is a strong contender in 2008).
In my humble opinion, Djokovic deserves the most improved player of the year. He worked hard, moved strongly up the rankings and ensconced himself firmly at #3, even though (in contrast to Nalbandian), he wilted at the end of the year. I expect him to start off 2008 strongly and sustain his level consistently, barring injuries.