Re: Sam Coupe
As a Sam owner and someone who has written software for it (no, nothing notable; my best effort) I think its problems were more about the spec than the launch.
There's no hardware scrolling and if you wanted to scroll the high quality display in its entirety it'd take four frames. So most of the then-current style of action and platform games are straight out unless you want to render them in the Spectrum graphics mode or the Timex-style Spectrum graphics mode but with separate attributes for each 8x1 block. Cue a slew of puzzle games.
With respect to the expected sales point re: the Spectrum, the paging scheme is entirely different from the 128k Spectrum so there's no way to run 128k games at all. That's in addition to the timing differences that make many Spectrum games fail to load (the Spectrum tape interface being essentially a 1-bit ADC that the CPU polls in carefully timed loops); and they declined to licence or otherwise replicate the Sinclair ROM so you're not getting even the Spectrum compatibility it can do out of the box.
Within a year of launch, prices were something like £200 for the Sam, £300 for the Atari ST. So at that point you're not even looking at good value for money, especially once software catalogues are factored in.
MGT were hobbled from the start by development budgets, I think. If you compare and contrast to the Atari Lynx of the same year, that had a quarter of the RAM but a faster CPU, a scaling blitter, a dedicated fixed point maths unit and a built-in LCD screen, for only about £130 — and that was before console manufacturers were in the habit of subsidising the hardware with future software sales.
Subjectively speaking though? I loved the little thing, and used it through to at least 1995. Both it and another I bought are likely still where I left them when I eventually went to university.