I recently upgraded from Mathematica 5 to Mathematica 8 and I have a number of notebooks that no longer work correctly. The problems relate to the use of units. I don't need complicated unit conversions so I typically just tag values with symbols for the units. Under Mathematica 5, I could write the following (I understand that this example isn't physically meaningful):
3. in + 4. in - 7. in + 5. lb
And Mathematica would return
Now, under Mathematica 8, I get
0. + 5. lb
This breaks a large number of notebooks. Can someone explain what is happening, and what if anything I can do to get the old behavior back?