A:Answer I have both the 7840 at the ES-580W, test set was a 4-page color document, 300 DPI scanned to emailed PDF:
Epson 7840, Simplex Scan: 35 Seconds
Epson 7840, Duplex Scan: 78 Seconds
ES-580W, Duplex Scan: 9 Seconds
I would not rely on this machine if I needed a lot of scans, the ES-580W is an excellent machine.