We're using a 10 gal gott cooler with a false-bottom for the smaller batches and a 80 qt rectanglar cooler with copper grid false bottom for the large batches. Channelling hasn't been an issue as the diluted wort is pumped onto the top of the grain bed and then gravity fed into the kettle.
Channeling depends on the layout of your mash tun. If you have a false bottom or copper manifold designed for fly sparging, you should get good efficiency with this method. Batch spargers with only a braid or bazooka T could see lower efficiency.
No-Sparge is supposed to create very high quality wort for rich malty beers, and I think this is basically the same thing. You could do a fly sparge with the same mash tun size, but you would need a third vessel to hold the sparge water, so this actually does make it easier. Perhaps this is something that most fly spargers should look into...
If you're having problems with wort quality with a regular sparge, I would definitely look into the bicarbonates in your water and possibly add acid to your sparge water to keep the pH down.