Hi,

In the past I've used Blackhole, the bundled syntax-case implementation and Alexpander.
Each one has its own advantages and disadvantages:

blackhole
- A: it works well, and not only syntax-rules, but also sc-macro-transformer and er-macro-transformer
- D: forces you to use its module system. I think this is a mistake, since is not standard, but anyway it has some current limitations for my work that I tried to fix in my own branch but stem from deep parts of blackhole that would require a deep understanding and rewrite. I tried that already and spent a fair amount of time working with Per these issues and decided to drop it.

syntax-case
- A: installed with Gambit, easy to setup, supports syntax-case? (I guess so, but haven't tried this last point as I don't really care at the moment)
- D: incompatible with DSSSL and other Gambit functionality. I really don't understand why the bundled implementation doesn't support it...

Alexpander
- A: it is supposed to support DSSSL and be nicer to Gambit
- D: I still get errors related to define-macros, even if they are not mixed with define-syntax macros. Taking into account that some of my macros work with both blackhole and syntax-case but not with alexpander, I assume this implementation is less mature/stable.

The point is: is there any stable, good implementation of R5RS syntax-rules that is fully-compatible and nice to all of Gambit's functionality?

I believe this should be a basic feature of the Gambit ecosystem, but maybe I'm missing something. 
Any help, ideas or opinions?

Best regards,

Álvaro Castro-Castilla