As far as BASIC goes, it blasted AmigaBasic out of the water (just remembered, Amigabasic was written by mickeysoft wasnt it? Hmm, explains a lot).
It was quick (esp. AmosPro & Compiler), had some real good functions in it (esp. sprite handling etc). Initially it was better than Blitz but I think Blitz took over later.
Amos just wasnt OS friendly (i.e. writing WB apps was a nightmare). I think because of that, you got mocked merely for knowing what it was. Shame. Was a good easy first step for getting into Amiga programming. Real good of quickly knocking up prototypes too.