13.1) What's the best DOS for the Atari?

This is a matter of opinion, but general consensus is that all 8-bit Atari
users should treat themselves to either MYDOS or SpartaDOS to appreciate the
power of the system.

Either MYDOS or SpartaDOS will work with almost any disk drive, up to 8
drives or hard disk partitions, and ramdisk.

MYDOS is modelled after Atari DOS 2.0S/2.5, but provides subdirectory and
hard-drive support.  MYDOS 4.53 is freeware from Wordmark Systems (Charles
Marslett and Bob Puff). There are two versions of MYDOS 4.53, one uses 3 digit
sector numbers where possible, known as 4.53/3; the other, known as 4.53/4,
uses 4 digits minimum.  Complete documentation about the disk formats and
commands, as well as the source code, is available.

SpartaDOS is a completely different command-line DOS modelled after MS-DOS,
though it is perfectly capable of reading all Atari DOS and MYDOS disks.
SpartaDOS 3.2g and 3.2gx are disk-based; SpartaDOS X 4.22 is cartridge-based
and includes many additional features.  SpartaDOS 3.3a and 3.3b were rewritten
by Stephen J. Carden for use with BBS Express PRO!.  SpartaDOS 3.3c is
available in a 16K ROM cartridge from Video 61 (see compantion Vendor List).

It is recommended that all 8-bit Atari users own at least DOS 2.5 for complete
compatibility with existing software, and then choose either SpartaDOS or MYDOS
as they see fit.  DOS 2.5, MYDOS and SpartaDOS are all available on the
archives.
  filenames:   Os/dos25.arc (DOS 2.5)
               Fte/fte32g.arc (SpartaDOS 3.2g)
               Os/mydos453.dcm (MYDOS - latest version)
               Os/mydos45m.arc (MYDOS - latest complete doc's)

Another popular, powerful DOS is BW-DOS, freeware by Jiri Bernasek.
BW-DOS 1.30 and all other versions are available via:
http://atari.boss.com.pl/files

Any other versions of DOS all 8-bit Atari users should be aware of??