There are a few changes made between 2000i2 and 2001. The most significant is that the show/erase menu for displaying the dimensions on drawing views has been moved to the View menu at the top of the main window (This will drive you insane if you haven't been told about it).
Also, many of the geometry generating functions can be accessed much more quickly from the menus at the top of the window than from the side menu.
There is a selection filter available too, which allows users to select edges, right click and fillet then dynamically, saving time on that function. There is also a dynamic modify menu (Hold down the right mouse button after selecting certain features and it makes drag handles appear). You can insert protrusions on preselected planes and surfaces too.
AFAIK the graphics engine has also been upgraded between the two versions, which allows the program to do seriously sick filleting without batting an eyelid.
Basically ProE 2001 is significantly more powerful than 2000i2 and well worth upgrading to.
It's scary to say, but forget everything you know about 2001, I just used Wildfire (2002), and it is really different. Much more slick, and efficient to use. Takes some getting used to, but worth it.
