I did a lot of tests today, with vSphere 5.0 and 5.5 (IBM Edition) and different 
versions of Grml including a daily build from last week. Same result for all 
setups: Boot hangs after "Waiting for /dev/". When ssh is enabled I can ssh into 
the machine so it's just the display driver which hangs or just stops to draw 
output.
With Grml's boot parameter noudev or without framebuffer everything works. I'm 
sure it's because of https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=714929
The bug report also mentions another workaround: Set kernel parameter 
vmwgfx.enable_fbdev=1. This worked for me, too.
So we could provide a file in modprobe.d with content "options vmwgfx 
enable_fbdev=1". But I'm not sure it that breaks anything.