I had a couple of problem areas that required re-coding to resolve.
First had to do with conditional formatting. In 2003 it was no problem when
my code made it possible to copy a cell with conditional formatting multiple
times to the same location. In 2007, it became completely unworkable. In
2007 the "feature" of copying conditional formatting causes the conditions to
simply be ADDED to the destination cell existing cf conditions. Intuitively
everyone seems to think it should REPLACE, but it just ain't so. Weird
things start to happen when you pile more and more conditions on top of a
single cell.
Second is the increased size limit of rows and columns and how that impacts
the speed of calculation. I've seen many reports of files that worked great
with 2003, and because of this issue, they slow down enough to cause big
headaches. If your code causes changes to cells that would trigger a
recalculation, then you'll want to set calculation mode to manual, and
explicitly perform the calculate action just when you need it. Takes a
little more thinking about where your code is drawing on calculated values
and whether they need to change in response to other steps.
Those are the main ones I know of, but I believe there are others as well.
Someone else can pitch in with what they know.
