I'm actually discovering that using key analysis can be extremely helpful when trying to mix together tracks, even when you're just relying on an analyser (using Pitch-n-Time from Serato myself). But I use it only as a tool, not as a be-all-end-all to mixing. It can help you find useful transitions between tracks and ways to get from point A to point B, but ultimately you have to rely on your ears, and if something isn't meshing, there may be no fixing it whatsoever and you just have to abandon the transition, or find some other way to move without making the harmonies clash.

But yeah, that whole bit about the different moods of the different keys had me clawing my eyes out, and made the guy pretty much lose me for the rest of the article.

I'm not on any extreme about key-mixing. The way I figure it, if it sounds right go for it. Everything that you use to get there is great, where it be focusing on camelot wheels, using key analysis and even using key shifts (WARNING: don't go up or down by much more than a half tone, or a full tone in some cases, or you're going to start sounding like shit), or if you just go by ear and let that guide you the whole way through, whatever you use is fine, but the trick is that it has to sound good. There's no point in making a shitty clashy-sounding mix and then be like "well, they both showed 12A on my camelot notation" because that's not how it works.