In July, we put up our first Windows Server 2008 server. Since then, I have migrated the domain from NT 4 to the new domain (which was upgraded from 2003 to 2008 too), put in Office Communications Server 2007 (OCS), Exchange 2007, SharePoint 2007, and I am in the process of getting Dynamics CRM 4.0 in place. After all of this, I think I can fairly report on Windows Server 2008.
First of all, it works, it works better than any other Microsoft OS I have encountered. They significantly cleaned up and reorganized the interface so that logically related tasks are "closer" to each other and are sometimes in the same tool now, as opposed to using 4 separate tools with wildly different interfaces to get things done. PowerShell is suddenly a "big deal", and many of the GUI management tools really are just wizards to construct & run PowerShell scripts on the fly (Exchange 2007 Management Console is a great example, it even shows you the PowerShell command it is about to run). Now that I've had to use PowerShell, I like it, but only because I am familiar with *Nix; it's like someone took the *Nix model of pipes and indirection, and instead of letting all of the commands be developed hodgepodge by different people with no common naming conventions, format conventions, etc., it was all centrally managed and therefore, logical.
Things I don't like? Application incompatability. A lot of apps (ISA, Office Communication Server) don't work on it. Others require odd modifications (Exchange 2007, pre-rollup 4, needed some bizarre hacks to disable IPv6 in some common scenarios) because the applications don't work "right" with it. I'm unhappy that Microsoft is pushing some products to 64-bit only (like Exchange 2007), while others refuse to run under 64-bit (Office Communication Server). This mandates that you have at least a 64-bit and a 32-bit install, and possibly (probably) a 32-bit Windows Server 2003 machine around too. I'm furious that many of the updated products are 64-bit only, which means that instead of a simple upgrade, you need to bring the new version into the "pool", transfer responsibility to it, then gracefully disable the old 32-bit server from the pool, and then uninstall it; this is the "upgrade" path for OCS 2007 R2, in a nutshell. And Exchange 2007, for that matter. Not a nice thing to do. Personally, I find that it is easier to see what my options are when they are in a GUI than a command line, I just walk the menu tree and go into every dialog. But that is a personal thing. At the same time, many tasks can only be done in PowerShell, so if you don't like the command line... tough.
Hyper-V ROCKS. I can't compare it to VMWare ESX server, but I can tell you that it beats VMWare Server, Virtual PC 2007, and Virtual Server 2005 with the ugly end of the ugly stick, and leaves them half dead in a Moscow alleyway. The biggest gripe I have, is that its missing features are in the (just RTMed) System Center Virtual Machine Manager product. Granted, much, if not most of that functionality is already available via PowerShell (once again, the idea that GUI tools are now just PowerShell script construction wizards). But still, it would have been nice to easily get P2V and V2V conversions up front with a GUI tool.
J.Ja