Can you describe the computationally heavy spreadsheets you made? How many cells, how many distinct formulas (i.e. distinct except for relative references), how

Can you describe the computationally heavy spreadsheets you made? How many cells, how many distinct formulas (i.e. distinct except for relative references), how many worksheets, how long it took to recalculate? Were you pushing any limits of Excel? Were there annoyances? (My email's in my profile if you'd rather discuss it offline.)