The following are some nice references that discuss how MES/MOM systems are used at the shop floor in manufacturing companies to complete the enterprise systems landscape on top of ERP systems. MES/MOM adoption is on the rise and several of these papers discuss trends and the reasons behind them.
Manufacturing Operations Management Report by Aberdeen
http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/ftalk-wp011_-en-e.pdf
Cambashi whitepaper sponsored by SAP - Foundation for MES/MOM Payback
http://www.plantservices.com/assets/wp_downloads/pdf/091014_SAP.pdf
Industry Directions – Whitepaper - Best of the Best Plants Use MES
http://www.glbinc.com/MES_Performance_Advantage.pdf