Metacomco, an acclaimed system software developer in the 68000 world, has done a good job with its ST Macro Assembler package. It is the only package to provide an example source listing of a program that makes GEM calls, but like the others provides no real documentation.
ED is Metacomco's standard, simple, full-screen TOS-based editor, and is similar to Micro EMACS. It is adequate for working with assembly language source files, but takes some getting used to. It has some nice features, such as the ability to specify the text buffer's size and to continue executing a command (such as search and replace) until an error condition arises.
The assembler came closest of the four to functioning as a replacement for DRI's AS68. It has all the features of GSTASM, plus local labels; but the macro facility is much weaker and no library of macros is provided. Strangely, two directives that do absolutely nothing are provided, yet there is no EVEN pseudo-op to make sure the following code begins at an even address. The manual documents the LINK68 linker, which is not supplied on the enclosed disk. However, the instructions for assembling the sample programs (provided in printed form only-aargh!) apply only to LINK68 and reference libraries not included on the disk. GST-LINK and its manual, identical to that in the GST-ASM package, are included. Metacomco's manual is typeset and carefully indexed, but does not accurately reflect the contents of the disk. This is a vanilla program-I suppose it lives up to its claim of being "full specification" but it is not as complete as GST-ASM.