Starting with ACAD 2004, Autodesk will not upgrade MDT. Your choices are mechanical 2004 (2D)and inventor (3D). I have MDT on my personal system and it has several limitions in regards to building 3D models from sketches especially when building gears. For example, I have to build one tooth on the 3D circle and extrude it and use polar 3D array. In ACAD, I build the whole gear and extrude.
Hope this helps,
John