I built myself a 400x400x500 CoreXY machine from scratch.
Honestly, my prints are dogshit unless I go slow, and then sometimes they're dogshit anyway. I have found the entire exercise as one of futility and massive frustration... but I low key love fucking with it. I can't help myself, I keep building upgrades and improvements for it. I keep sinking time and energy I don't have (and cash that I do) into this fucking heap of shit and I can't help but love it to pieces. It's dumb as fuck and it's pretty fun to work on.
Honestly the vibes are about the same for a project car. Don't daily it or you will hate yourself, but if you put it together and tune it right, you'll have a blast.