I'm running an interesting test on a PC of Excel 2003 and Excel 2007.  I ran
a Monte Carlo simulation in Excel 2003.  The workbook has 50 input cells
(cells where random values per distributions are input) and 200 calculation
(formula) cells.  So, it is basically a small workbook.  No conditional
formatting.  No charts.  The VBA code calculates random values per
distributions and puts into the input cells.  The workbook is then
recalculated and the values of the input and output cells (20 of the formula
cells) are recorded.  Only cell values are recorded - formatting is not set
on the cells until the end of the simulation.  No copy and pasting is done.
The PC has a 1.6 GHz processor and 1GB of ram running Windows XP.

With Excel 2003, 2,000 simulations were done in a minute.  For 10,000
simulations, typically minimum I run, it took five minutes.

With Excel 2007 100 simulations took a minute to run.   To do 1,000
simulations takes 10 minutes.  To do 2,000 simulations takes 20 minutes.  I
haven't finished the 10,000 simulations - it will take close to two hours
for it run.   I'm going to go to dinner first.  Which is why I said in the
first paragraph that I was running an interesting test - it is still running
(perhaps I should say crawling, but that is too fast of a word)

My conclusion is obvious.  Excel 2007 is lower than molasses on a cold
winter's day. It takes 20X longer to do the same task of calculate and
record.  And this is without charts, which I understand from other posters
really slows Excel down.

Bob Flanagan
Macro Systems
Productivity add-ins and downloadable books on VB macros for Excel