I’ve been on the fence about getting a Lego Boost for my five year old as well. Your comment made me pull the trigger finally, thanks!
The fact that my 5 year old likes to build lego and is interested in robots is a nice bonus :D
And if your five-year old is anything like mine, brace yourself for the noise it can make :-) (most programming she is doing on her own are the embedded activities that produce music, sounds, e.t.c.)