This is what I've done(on my HP's) but plan on doing the same on my dell's..
The only reason mine is 20GB used is because of /vmimages.. I have a bunch of iso's there. If you're using a SAN for your VMFS... just throw everything at root and split off /var and /opt to smaller sizes so they can be contained..
I like having it all in / because then I can use vmimages as the rest of my disk and not really have to worry about how "big" my / is
# vdf -h
Filesystem Size Used Avail Use% Mounted on
/dev/cciss/c0d0p6 124G 20G 97G 18% /
/dev/cciss/c0d0p1 244M 30M 201M 13% /boot
/dev/cciss/c0d0p3 3.9G 75M 3.6G 2% /opt
none 391M 0 391M 0% /dev/shm
/dev/cciss/c0d0p2 5.8G 224M 5.3G 4% /var
/vmfs/devices 814G 0 814G 0% /vmfs/devices
/vmfs/volumes/4643eb73-018e4270-72ed-001b782f773a
304G 238G 65G 78% /vmfs/volumes/esx1_1
/vmfs/volumes/464d5cd5-682ab27c-ab60-001b782f773a
9.8G 8.6G 1.1G 88% /vmfs/volumes/esx1_2
/vmfs/volumes/47c8c330-cdf71dc0-70ae-001b782f773a
29G 8.6G 21G 28% /vmfs/volumes/esx1_3
#