Here's the press release direct from Boeing:

Boeing Next-Generation 737 Gets a Face-Lift

SEATTLE, Jan. 26, 2005 -- Boeing [NYSE:BA] this week rolled out its first 737 without eyebrow windows, the four small windows above the front windshield. In the past the eyebrow windows helped provide better crew visibility, but today's advanced navigation systems have made those windows obsolete. The design change reduces airplane weight by 20 pounds and eliminates approximately 300 hours of periodic inspections per airplane. Retrofit kits to cover eyebrow windows will be available mid-2006 for the in-service 737 fleet.

Boeing: Boeing Next-Generation 737 Gets a Face-Lift