Competively speaking, natures are a great addition to the series. It allows people to customize their pokemon's stat to fit their purpose much better.
However, ingame, I have many gripes with this system. It's annoying that you need to get a bit lucky to have a nature that doesn't get in a pokemon's way. Caught a Abra? Oh, wait, it's adamant, and as a result, it isn't nearly as useful as a normal abra would be.
For normal pokemon, this can be a little annoying, but you always are able to overcome it with enough patience. However, playing soulsilver, both my lugia and raikou got natures that nerfed their best stats in favor of much less imporant ones. Once you save, this is permanent. Synchronize helps, but even then, it's a 50 % percent chance on a pokemon that could take a good while to capture.
For getting a competive pokemon, you either need a everstone, or it's heavily luck based. Even with a everstone it takes some setup.
The idea is good. But the random execution of it annoys me to no end.
Is there any possiblity of the system being less random, or the concept being transferred to something non-random?