I'm a veteran of Death Tank Zwei, and I've entirely fallen in love with Death Tank XBLA. I've mastered most of the new or changed weapons, but I still can't successfully use the missiles with any consistency.

On DTZ, the missiles were simply steered left and right. In DTX, they're a bit more complex- they try their hardest to go wherever you point with the left analog stick. Whilst I can see that, in theory, this would let you pull off some truly amazing shots, and even hover the missiles overhead waiting for the right time to strike, in practice all I seem to do is spin them in a circle and then hit either a mountain or my own face.

Has anyone mastered the DTX missiles? Any advice?

It's been a while since you posted this, so you've probably figured out the trick by now; practice.
I wouldn't say I've mastered them (I certainly don't have the related Achievement for their use), but in Arcade mode I can knock down the aerial mines with a high degree of accuracy. I'm wondering if I'd do better with the old control scheme as I'm more used to that.