At first listen, I was a bit disappointed with this record, since I'm so inclined towards obvious progression from album to album by any artist -- Tim Hecker's style is immediately identifiable (even if he's sick of hearing that "Fennesz with less presence" comparison, it's pretty accurate), and as someone who has only just begun to really immerse himself in ambient, I'm only beginning to pick up on detailed, subtle differences between ambient recordings, and truthfully, the details and subjective aesthetic interpretations are where the differences between this disc and its predecessors lie.
The overall mastering/equalization of Mirages is pretty similar to that of ...Radio Amor, with huge spikes in the midrange frequencies, giving the whole album a warm/foggy quality. Despite this (or maybe even in spite of), the overall feel of the album is darker than that of ...Radio Amor, having nocturnal overtones similar to that of Haunt Me, Haunt Me, Do It Again. These production elements and the overall aesthetic feel coupled with the tendency for more reverb/less presence (the depth and resonance of the production on this disc are absolutely chasm-like) on Hecker's behalf on this particular album call to mind a humid, sleepless summer night.
Mirages ultimately comes off as bittersweet and melancholy through a bit different of an approach than through what Haunt Me... uses -- Hecker's trademark fuzz and glitch work that is so often likened to Fennesz is softened here, separating himself moreso from Fennesz. The result is an album that is more personal, albeit more accessible (Tim Hecker's love of glitch has always been pretty abrasive and abrupt; here it is used more subtley). A highly recommended HEADPHONES album.