New Scientist did some digging after yesterday's hypo-allergenic cat story broke. What they found was rather interesting:

It is probably possible to create cats that do not produce the most common protein allergen, says Thomas Platts-Mills, director of the asthma and allergic disease center at the University of Virginia in Charlottesville, US. But he adds that cats produce many more allergens, and that blocking production of the protein could damage the cat's health.

Which is more or less what I expected. From my admittedly limited readings, allergic reactions seem to be damned complicated things, and claims that a single alteration (no matter how gee-whiz) can cure them sounds mighty suspicious to me. But it gets better:

[Allerca's] parent company, Geneticas Life Sciences, has a division called Genetiate which proposes adding jellyfish genes to deer so their hair and skins fluoresce when illuminated by car headlights. The sight of glowing green deer would bring drivers to a screeching halt, avoiding accidents.

Which sounds so wacky I'd normally chalk it up to a government program. It's rather rare to find people actually spending their own money on something this screwy.

Bottom line: like the article says, don't hold your breath waiting on super-kitty.