360 degree radial speakers and imaging...

At frequencies above 1500 Hz, the ears derive directional cues primarily by relative intensity, rather than by arrival time. So if you have an omnidirectional system, you want to make sure that early reflected energy is fairly well diffused so you don't get a distinct, image-shifting reflection (absorb too much, though, and the system can sound dull). Arrival time still plays a role in image localization above 1500 Hz, and is the primary source of localization cues below 1500 Hz, so the longer the delay between the direct sound and onset of reflections, the better the imaging will be.

Omnidirectional speakers do a very good job with intrumental textures and timbres, because they more closely mimic the radiation characteristics of live instruments. Obviously there is a tradeoff of image precision for lushness and enveloping ambience. Although I don't own or sell any omnidirectional designs, I readily concede that a well-executed omni (like an Ohm F or MBL Radialstrahler or Wolcott Omnisphere) or quasi-omni (Shahinian Diapason) is extremely enjoyable long-term.

Also depends on which "omnidirectional" design you are referring to-some put too much emphasis on reflected sound and end up sounding like Bose.

Rny, Rcprince and Thorman hit it all on the head. Just don't expect "realism" without a lot of horsepower. Sean
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I had the oportunity awhile back to hear the MBL $30,000 omni directional speaker being driven by MBL Monos'. Given the proper set-up ( which they were ) they sounded truly amazing.The most amazing to me was the sonically dissapearing cabinets and natural tonal balance of music.Unfortunately they come at a price and also need much current to reach there full potential.

The best of them can indeed create a holographic soundstage which you can actually walk into the soundstage or "view" it from any location in the room without worrying about a sweet spot (mbl's are great at this, as were the original Ohm Walsh speakers and, to some extent, my speakers, though they're not a true omnidirectional design). Channel separation is not a problem at all. Pinpoint imaging is not as pronounced as with conventional designs, though--the images are there, extremely palpable and three-dimensional, but perhaps a little more diffuse than you might be used to. On multi-miked and pop recordings this can be a bit disconcerting; on well-recorded material, particularly where there is a large soundspace recorded, it can be surprisingly realistic.

I believe with adequate spacing between speakers, left and right channel separation remains consistent with other designs. The potential benefit of omni-directional sources is the ability to create an image which can be palpable from an expanded listening area, as opposed to a listening position.