Does anyone have experience with this / know of resources for making a good investment? Or am I way over-thinking this and just some regular Legos or art supplies are going to do essentially just as much good?

I bought some sciency toys for my little brother (he was probably around the same age), like a kit for making crystals etc. - but that didn't get nearly as played with as regular Legos. Lego Technic are probably a good compromise towards Mindstorm (I get the impression those would be a bit complicated for an 8-year-old), though as a kif I remember having more fun with regular Legos than with Technic (yes, now I could build neater stuff with them, but a kid may be less likely to do so spontaneously).

I would rather have my kid play with Legos than play with a computer, even an EDUbuntu computer, but I don't know how well grounded that gut feeling is now (my kid is way too small for me to worry about that now). I'll have to research it more in depth eventually.