I've only read through the first 8 pages of this thread so far so I apologize if this has already been covered but the huge British ale company, Marstons is using this technology commercially currently. The pubs really love it. They use it for what may be it's ideal practical brewery application: cask ale.
The downsides of the technology seem to be fermentation performance; but that's not such a big deal when your secondary fermentation is occurring out of your expensive clyndro conicals and in casks on the way to pubs. Pubs hate the beer losses and excess yeast that often end up in cask ale, but people like that the beer is still "living" and the yeast are still conditioning the beer and producing CO2; these yeast balls solve the problem as the beer is both clear and alive and producing CO2.
See
www.fastcask.com for Marston's page on their application of the tech.
This is a great technology to use for secondary conditioning even for homebrewers. We can crash cool after primary fermentation is complete and then transfer the clear beer into a corney keg for cold or warm conditioning with yeast. I think it could also be great for lagering in a keg that you're already serving from especially if the yeast balls are added to a stainless tea strainer as someone already mentioned. I LOVE that FANTASTIC well-conditioned flavor that you get from a really long slow lagered lager, or a kellerbier after the yeast finally drops but I don't want to keep transferring off of the yeast or sucking up yeast in my keg dip tube.
This is a great technology for all secondary fermentation, IMHO. People HATE that home brew often has a bunch of yeast in the bottle; if you add 3 yeast balls to each beer when bottling you can easily leave them behind in the bottle and get out 98% of the nice clear beer.
We know that there's no oxygen scavenging technology that works better than live yeast.
Adam