I remember the PET. I saw some at the computer club I went to in the early 80s along with various other machines. They were mostly incompatible with each other.
We take lots of memory and a fast CPU for granted these days, but you had to code efficiently in those days. I saw someone give a talk on programming the Atari VCS that was really under-powered. You had to be really clever to get a playable game running.
I did mostly BASIC on my Beeb, but tried some assembler.
Yeah the 2600 is a real pain, you have to "race the beam" (as in the CRT drawing the screen) which means to get anything done your code has to be super, super efficient. And yet they produced a BASIC cart for it!