I've never fitted headangle reducer cups, but my cyclus one is waaaaay better than the B&Q verion I had before, whatever permutation of washers/spacers etc.
Its the stepped cups with a long 'shaft' to keep it straight on the on the threaded rod part on the proper tool that make it go in straight every time (I wonder if it didn't have the right sized 'step' on it for northwind's headangle reducer). Difficult to keep a stack of washers perpendicular to the threaded rod in the DIY one if you have a headset cup that keeps wanting to go in on the wonk.
The fine pitch thread is also better for the snugger fitting headtubes than a big m10 threaded rod too. Mine has done four of mine and wife's bikes plus three or four of my mates' ones so far. Little difference if your headset can go 3/4 way in by hand, but greeeat for more stubborn fitting ones.
All that said, the DIY one would be functionally about the same as a proper one with the addition of some home made machined stepped 'cups' and a thrust bearing to go under the bolt you tighten up. There must be someone on here that would machine off a bunch of cups in their garage and buy the other bits in bulk?