Not 24/7/365...but I've done alot of intercompany benchmarking of integrated systems for supply chain..which covers quite a bit of ERP territory.

When implemented correctly, ERP systems (SAP mostly in my experience) allowed some very good business practices to be developed and made moving to the connected world very simple for these companies. The leading implementations in the chem industry that I saw all went very early into web enabled jit inventory and purchasing systems, allowed these companies to offer creative solutions to customers such as managed inventory (vmi)...high quality stuff.

I also saw my company's implementation of SAP fail miserably to produce an adequate roi on the nearly 60 million invested.