It is defiantly worth every penny if you are planning to use it fully.
64bit is especially good if you are doing 3D stuff like Maya, play games with great graphics or video they all will become faster and look better.
Well Maya isn't out a as 64bit program so it wouldn't make all that much difference. With any luck the next Maya upgrade should be around May and i'm hoping it will be 64bit.
Lightwave now has a 64bit version.