Changes in functionality from W2K3 to W2K8
Anyone contemplating deployment, evaluation etc. of Server 2008 should read the Microsoft document over at [http://www.microsoft.com/downloads/details.aspx?FamilyID=173e6e9b-4d3e-4fd4-a2cf-73684fa46b60&DisplayLang=en] which details in 336 pages the changes you will encounter on your journey from Server 2003. A good document I am reading yet again as it like Server 2008 itself still beta so keep an eye out for changes as they happen.
Those of you still using Windows 2000 are in for a lot more work I am afraid as although the changes, in my opinion, from Server 2000 to Server 2003 and from Server 2003 to Server 2008 are not insurmountable my gut instinct is that Windows 2000 'shops' are going to feel some real pain going from Server 2000 to Server 2008 unless they prepare.
One of my current projects has been working through the Microsoft Software Lifecycle [http://support.microsoft.com/gp/lifeselect] and 2010 will be an interesting year, interesting as in the Chinese curse of "may you live in interesting times". Server 2000 will exit Extended support in 2010 and effectively be unsupported and Server 2003 will have transitioned from Mainstream to Extended support as well based on the assumption that Server 2008 will indeed ship in 2008.
Leaving the big question for organisations still using Server 2000, not a small number in my experience here in the UK, what will be your strategy? If you and your organisation do not have at least a plan get one and be prepared to revise it as time moves forward which takes me back to the Microsoft document on changed functionality - reading this and understanding one of the options for your organisations future comes highly recommended.