Excel as a graphing/charting app is a very blunt instrument. Dedicated charting apps are far superior.
OmniGraphSketcher's forté is not graphing
Excel data; its forté is generating graphs that look like the work of a professional graphic artist. At $29.95, it is one of the best bargains in the professional software market. If graphing
Excel data is your intent, then
DeltaGraph is the traditional choice. Its graphs are probably the best combination of design aesthetics and technical precision on the market.