Network Document Scanner Advice

I need a network capable scanner and know almost nothing about these devices. I know I would like to be able to:

• plug it into my LAN
• scan multiple pages (up to 30) in black & white
• scan to a network folder
• scan in PDF format.

This thing will get hammered on a daily basis, like 300 to 500 pages a day in groups of 5 to 30 pages.

Has anyone got one in their office and used it with success? If so what brand and model? What are some of the cons of the unit you use?

--Jon