It seems that I am not the only one who has noted that complex spreadsheets often contain errors. Apparently errors in complex spreadsheets have resulted in several major accounting problems at large corporations (one of the errors was by over $1.2bn). Other relevant info here.

I'll stick with python and sage for my data analysis. All the equations are sitting out there staring you in the face, rather than hiding out of sight in all those cells. Spreadsheets are a lot easier to learn though, so I understand why they are so popular.