I don't believe it is the best but I do feel it is very important to the series as a whole. It seems the most complete of the FF worlds and this may in fact be it's true strong point. The music, I will agree is not nearly as memorable as some of the composer's previous work but it at least works for the feel of the game. There are no bad tracks, it's just not memorable.
I won't argue about the cast and plot cause I've been doing that in two other threads now. I do find that alot of people miss out and judge it too quickly cause it's not nearly as melodramatic as the past FF's. It is just told in a very sutle way. I feel you have to read between the lines a little more and watch the characters reaction while talking to gain insight into them. Of course even I'll admit that I may also be reading too much into everything and most of what I feel is really going on is in my head
It is nearly flawless as a game once you get used to the new system. It's only glaring faults are the basic problem you find in most MMO's which is grinding, though FFXII does a slightly better job in fixing this issue, it is still there .
My only hope is that SE will remember the strengths of this game when it starts to work on the next game. It is definetly the best of the PS2 FF's no contest.