Great blog!
I've dabbled in 15mm quite a bit, and ran a whole RPG campaign in which we used 15mm throughout. I've also painted up a couple of HotT armies in the scale, and various 15mm sci-fi things.
For fantasy, though, I've largely abandoned 15mm for 28mm on the one hand and 1/72 on the other. Why? Well, I found that one 15mm figure didn't take much less time than a rank-or-file 28mm equivalent, and that the fiddliness of multiple bases was actually greater with 15mm than with 28mm or 1/72.
Also, where 1/72 wins out is on consistency of scale. Yes, there are some variations, but you can mix and match 1/72 much more freely than with 15mm, where the size of humans and horses fluctuates widely. Some 15mm goblins and dwarves actually work better with 1/72 than with 15mm (unless you want your dwarves and goblins as tall or taller than men!).
I think 10mm enjoys the same advantage - at least to some extent and possibly because there are fewer manufacturers.
Anyway, your 15mm stuff looks brilliant!