The 16K-RAM and original 48K-RAM "Speccy" models' keyboard was lovingly described as
"dead flesh" due to its feel. DKTronics made
replacement keyboards with
proper keys, and later 48K Spectrums (the "Spectrum +
48K") were released with rounded-key keyboards (as seen
on the QL, I believe).
Early 128K Spectrums were released by Sinclair Research, and featured sound chips (like the Amiga's),
VDU and keypad connectors, a ramdisk, "calculator" mode, "tape tester", test card screen, and 48K-mode for the more obstinate
games. They had a Spectrum Plus-style keyboard, with all the 48K-mode keywords on, and an additional heatsink
down the side. The BASIC interpreter was still
with a couple of new additional commands (PLAY, to drive
the sound chip, being one of
them), but the new full-screen editor did the
tokenisation for you.
However, the Sinclair Research bubble was soon to burst,
and Alan Sugar (of Amstrad fame) took over production
of the 128K spectrum, as it shared the same Z80 CPU
CPC range of computers. For cheapness'
sake, the "Spectrum 128+2", "Spectrum 128+3" and "Spectrum
128+2A" also shared the same keyboards with integrated
tape drives (which were notoriously unreliable) and
disk drives (which were the doomed 3in-wide variety).
(Re-)design issues meant the pinouts on the
expansion ports differed in subtly incompatible manners
between models, and the new cases meant some
peripherals were no longer connectable anyway.