VMWare Player drivers are still unsigned, so the only way to run them on Windows Server 2008 x64 is to accept unsigned drivers on boot time.
More: Windows Server 2008 uses too much memory, so I have looked for an alternative. The answer was dual booting with a stripped down version of VMWare: TinyXP.
Yes, I know, TinyXP is now as legal as it should, but what the hell, I do own a legal XP license.
Installing TinyXP was quiet simple. The stripped down version uses only 50MB of memory - 42MB without explorer. After installing NVIDEA and wireless drivers, and replacing explorer with VMWare console (HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\Current Version\WinLogon Shell), I have a minimalist VMWare host.
I had an option that I didn't try out: Linux. Though legal, I have some doubts about sync/clocking problems, drivers performance, and I'm afraid I wouldn't use less memory.
And having an XP around to solve x64 incompatible drivers / apps is a must!