My oldest's math skills have really flourished on Dreambox, and my youngest is essentially teaching herself to read faster than I can on ABC Mouse. Plus the crappy wireless has taught my oldest daughter to diagnose wifi problems :).
They love taking pictures of themselves with the webcam, and I don't have to worry about them messing it up. It's on a little table in the living room where I can easily supervise, and they love "working" while I do work on my laptop.
I maxed out the ram and installed an SSD and it's pretty snappy now. That was well worth the $ and effort.
I test the code on a Raspberry Pi connected to my LAN that's set up similar to my production web server and move it over when it's ready.
I really have no motivation to buy a new Mac yet after upgrading it. I'm not a gamer and I don't do video/sound editing on it, I just use it to write code and keep up with daily chores, so a newer, faster, more expensive, Mac isn't really going to do much for me.