Just for the record, I will answer your questions based on Ghost (the Enterprise Edition),
Not their consumer product with the same name which has derived from "PowerQuest Drive Image" but has got in common with the 'real deal'.
Can Norton image Linux partitions as
well?
Yes, Symantec Ghost added support for the ext2 filesystem in 1999 and for ext3 subsequently.
Does it mean that images can only be
created from within a running Windows?
No, Ghost.exe works in a DOS environment, however, for better controller controller support I recommend Ghost32.exe from within a Windows environment (e.g. BartPE)
For Windows partitions: Does it
support both regular and Server
versions? Acronis doesn't image Server
partitions in the regular version.
Symantec Ghost will clone any Windows drive/partition (even when encrypted with BitLocker, but Ghost will switch to 'sector mode' and the images will be accordingly large in size).
When restoring an image, does Norton
give the option of including/excluding the MBR?
The command line switch -PMBR specifies that the master boot record of the destination disk be preserved when performing a Disk-to-Disk or Image-to-Disk operation.
For more information about Ghost, I recommend the Radified Guide to Norton Ghost:
This guide presents what many consider
the ultimate back-up strategy. It is
based on features found in Norton
Ghost, a hard drive imaging/cloning
software program developed by
Symantec.
Although designed around Norton Ghost
(considered the most reliable
application of its kind), the
strategies presented here (such as
performing a test-restore, to ensure
your back-up image will work when you
really need it) can be applied to
any disk cloning program.
On a personal note: I have cloned thousands of drives with Ghost, it never failed me. Ghost is still the reference and 'industry standard'. the only program I consider anywhere near Ghost would be Drive Snapshot.