New multi-monitor features are the ability to set the primary monitor from Display Properties, and support for hardware-accelerated OpenGL (if the OpenGL ICD of the video card(s) supports it. See the list in the OpenGL FAQ). Here's how Display Properties looks like (note the checkbox near the bottom for setting the primary):

Also new: the popup which shows you the coordinates of the top-left corner of the monitor.

Setting the primary monitor this way works fine, except for DOS fullscreen applications (including a fullscreen command prompt). These applications always open on the monitor which received BIOS messages during booting (the primary monitor as set by the BIOS).

Other differences between Windows 2000 and Windows 98:

	Windows 98	Windows 2000
Disabling secondary monitor:	Monitor gets turned off	Monitor stays on
Boot message on secondary monitor?	Yes	No

Click here to see if Microsoft officially supports your video card for Windows 2000 multi-monitor.

Windows 2000: any good?
I would say yes. Think of it as a marriage between Windows 98 and NT 4, with an improved user interface (the new fade-in effect for menus and the shadowed cursors look great). Setup was rather painful, but probably because of incomplete ACPI support in the BIOS. Once I had turned ACPI off everything worked great.

I was using Windows 2000 Beta 3, Build 2031, with two Diamond Fire GL 1000 Pro video cards (one AGP, one PCI), using the default Windows 2000 drivers.