I am indeed that guy. I don't sell transformers though, so don't think I'm biased! On that front:
You can buy a 1:1 line level transformer for under $10 (I think, I don't have a link). However, a "basic" Lundahl LL1527 will run you $67, while their "best" the LL7902 will set you back $235. Remember that you need a stereo pair! I don't know for sure, but I bet if you asked them for an isolation transformer for a high quality audio application, their recommendation would be either that $235 unit, or something close to it. Lundahl is certainly not the most expensive winder either, they tend to be pretty reasonable!
Then, ask yourself, if a $10 transformer works fine, why would anyone need a $235 one? Remember, this $235 unit isn't for tweaky über-high end stuff, it's just the right piece for good audio (which is surely what all of us on this board are after!). The answer is that the $10 unit wouldn't really work fine. It would be very bandwidth limited (softer?) and might introduce some nasty phase problems and high frequency resonance.
Here's an example of where those IC's would be handy: You've got a grounded preamp/amp and you introduce a subwoofer connected at line level. Many sub plate amps are grounded. Then you've got a loop, and probably a 60hz hum that gives you fits. Some would "float" one of the grounds (I have), but that is a safety breach. The better solution is to leave the earth ground bonded firmly to the chassis of one of the units but insert a resistor between the safety earth and signal grounds. The difference in potential will probably kill the hum. But, if you aren't comfortable with modding your grounding scheme and you don't want to compromise safety of your system, using the IC's with the transformer will also solve your problem. Provided, of course, you've still got enough bandwidth to be satisfied with your sub! (Though given the relatively lower demands of resolution, if the IC's are transparent anywhere, it will probably be here).
The other common ground loop problem stems from CATV connections. But, the best way to solve those (IMO) is with an isolation transformer on the CATV line.
Which isn't to say that I wouldn't enjoy playing with those IC's. I like toys. That's why I sell a few speakers!
Paul