I used them as I'm often bringing tools I thought would be rarely used from their place on the cellar wall cleats up to the workshop wall cleats. Of course, I ought to take some of the tools I wrongly thought would be often used back downstairs, but ...
My experience was that you don't have to get the angle exactly 45° but you do have to use the two pieces (44° and 46° for example) as pairs. Which went wrong for me with my using two sets of cleats, when the angle changed in between uses of the saw; so exactly 45° turned out to be best for my purposes. If I was using a circular saw rather than the table saw, I'd go for measuring the angle of a test cut.
I used fairly crappy 19mm plywood; which didn't work too well. The problem is that the cleats come to a point; and if there happens to be a void or a flaky veneer at the point it's not so effective. So for the next round of cleats I'll use the better stuff, but probably not the best.
And it's not totally magical, they do rely - for the heavier and the cantilevered items at least - on the wood piece that's attached to the free cleat* hanging over the flat of the fixed cleat by a fair amount - say 15 to 20mm.
On the whole I'm very pleased with them; very glad not to be using pegboard any more.
* The piece that actually carries the hooks, the dowels, the holes, whatever.