It's not that I don't grasp the concept. I just feel like it's adding too many extra steps to what's as simple as math? ... probably the same reason why I (and DS5) have serious issues with Kindergarten homework. It's too much hands on and not much math that would move us forward.
Can your DS5 do arithmetic in arbitrary base? For example if you tell him that on Planet Zog the inhabitants have three digits* on each hand rather than five, so they do arithmetic with six playing the role ten plays for us, and then you show him a couple of two-digit example sums, can he immediately do multidigit addition and subtraction as reliably in base 6 as in base 10? For my DS there was a stage when he was quite reliable in base 10 but would get completely confused in any other base.
But I never bought manipulatives for him unless you count the linking elephants or the jar of counters, both bought when he was a baby and used occasionally for maths. For child-me, the Dienes stuff was tactically appealing (it used to be natural wood in those days!) and the multi-base stuff was a fascinating start for enrichment (I remember being asked to design a machine that would do sums taking input using blocks - remember this was before even calculators were familiar objects, never mind computers!). My teachers never, that I remember, made me use the blocks if I didn't want to. So I remember them with affection.
*if he's anything like mine this is necessary to let you opt out of a finger/thumb discussion
