Here is a review of the Mirage OMD-15s for Ultra Audio and here is a review of the Mirage OMD-28s from SoundStageAV.com.
Everything they say is true. The OMD series provides a better radiating pattern than simple wide dispersion or a purely omnidirectional speaker. The Omniguide's proportions of front, side, and rearward dispersion make for a realistic, scalable soundstage, plenty of soundstage depth, and more image specificity than you get with a bipolar or typical omni pattern.
Everything they say is true. The OMD series provides a better radiating pattern than simple wide dispersion or a purely omnidirectional speaker. The Omniguide's proportions of front, side, and rearward dispersion make for a realistic, scalable soundstage, plenty of soundstage depth, and more image specificity than you get with a bipolar or typical omni pattern.