Hmm... Where can I start? Maybe I'm biased since I have been using it since Beta3, and since RC1 I haven't used any other OS. All my machines(5) are running some build of Windows 2000.
Let me point out some things from the management of anything perspective, COM+(Component Services), Terminal services has greatly improved, Console Management for just about everythign under the sun. ADSI, easier to find just about anything as long as it's been added to it. Fresh UI, little things added here and there, like layered windows. Network management is alot easier, from domain names, to VPN's. Not to mention driver support, I bought a USB zip drive to take from home to work and Windows 2000 instantly recognized it and didn't have to worry about how I was gonna get the 14mb of utitities and drivers from Iomega's website to my machine that was not connected to a network or the internet.
Performance perspective, easier to upgrade to multi processors then in NT4. replace the hal through the device manager, reboot and whala... multiple processors, was hard to locate but once I did it was easy to update. Has crashed ever except for installing NT4 drivers or 98 drivers on it since everything is code signed now. Cluster services, WLBS. Object pooling now works in MTS. MSMQ has been greatly enhanced, no need to have SQL 6.5 installed anymore.
Development perspective, a lot more COM interfaces, which allow a fresh development of new applications and utitlities. I am working on a few on the side right now.
As you can tell I am very happy with it, but people may think I am very biased; because even though I don't work for MS, I have worked on many of their Windows 2000 projects in the past 9 months.
I have also recently finished a investigative report to determine the time, resources and rampup neccessary to port an exisiting multi-tier NT4 system to Windows 2000. The report turned out well; there was only one issue and that was with code not the components or system being used under Windows 2000.
I actually surprised myself when I decided I liked Win 2K. I say surprised because I absolutely *hate* using NT 4. I'll take 9x any day of the week, because NT 4 seems so clunky despite having the Newshell interface. (As one of my coworkers once put it, "NT 3.5: New technology, old interface. NT 4: New interface, old technology.")
I was pretty impressed with the PnP support (another reason I hate NT 4 - try finding where to configure hardware or interrupts sometime). Yesterday I hooked up a second monitor to make it easier to debug some GUI code, and when I stuck in the second video card it worked without a hitch.
The downsides are: You need a lot of disk space (the base OS install takes something insane like half a gig), and a pretty manly system. I just installed it on my home system to see how it would run - it's a Celeron 300A@375, 64MB RAM, 12G Quantum Fireball - and while 2K didn't run dog-slow, it was too slow for me to stand.
Another bad thing is... MS moved everything around!! I *still* haven't found the 2K equivalent of the NT 4 device drivers control panel applet. You can get to the services list, but not the device drivers. grrr. Luckily there are service control apps here that do the job.
The Device Driver control list is where you would find it under Windows 9x.
Right click My Computer. Click Properties on Context menu. Click the Hardware Tab of the System Properties sheet, click the Device Manager button in the middle of the property page.
File menu "Console", then click "Add/Remove Snapin". On the "stand alone" property page click "add", select "Device Manager" snap-in", click "add". Decide if you want to view a different computer. Then click "close", then click "ok".
Wallah, Presto. Device Manager. Now you can save the console session to your desktop for quick access.
I received an evaluation copy when I went to the one of the launch events. Apart from some problems related to drivers for my CDROM and Soundcard needing updates (unavailble at the moment) it runs fine on an old(ish) system (AMD K5-200 96Mb memory). The first thing that caught my eye was the slight shadow that the cursor casts on the desktop, giving an illusion of depth (I'm easily pleased!!!). I haven't run it long enough for the adaptive menus to kick in. I also haven't had a chance to develop on it either. In general, the Plug and Play hardware was detected straightaway during the install.
I think the major improvements will be on the Server side. The Professional edition looks very juicy for a laptop (NT security and stability, Win 98 power management, support for PnP, USB and IR transfers). I've been looking at the laptop vendors in the UK though, and although they are selling pre-installed Windows2000 machines, I haven't found one with a built in DVD-ROM rather than a CDROM