TBG, I agree that is the consensus, and that consensus has merit. Horns are very likely to impart additional colorations to the sound, due to the nature of their operation. However, if the horn design is very good, the colorations can be minimal, and the improvement of efficiency, and its attendant improvements is producing deep detail, can outweigh any minimal colorations imparted(at least with some listeners).
All speakers, no matter what design, will impart colorations to the sound. The key is to have the colorations not intrude significantly into your sensitivities, while still achieving other important aspects of producing your sound. All in audio is a trade-off. No free lunch. Sometimes you make a small sacrifice in one area, to achieve superior results in another area which may be more important to you as a listener.
While this may seem both obvious, and vague, at the same time, it is one of the most important things for any audiophile to realize. Nothing is perfect. The key to your listening happiness is to maximize the things that are most important to your sensitivities as a listener, while making the smalles sacrifices possible in the areas of less importance to your listening sensitivites. This is different for different people. That is why some are in nirvana with a certain system, and others couldn't even stand to listen to it.
Generally, with horns, the efficiency level is improved to the point that you require much less amplifier power to achieve desired SPL, which makes the amplifier less strained and improves the sound of the amp. Also, dynamic range is improved, as well as low-level detail. If the horn doesn't make any objectionable colorations to you personally, then it is good enough, being that you are achieving these other benefits. One of the really limiting factors of horns occur in the bass, where proper horn size is too large to fit into the listening room, and engineering compromises are made for compactness, that hurts the performance of the bass horn. The result is that deep bass is not readily achievable out of a compact bass horn. This makes designers resort to non-horn bass drivers, and then integration problems occur, where the bass is not as "fast" as the rest of the spectrum. These are just some of the difficulties that designers face, in trying to make these horn systems.
Basically, a horn is an impedance-coupling device to more efficiently couple the driver motion to the surrounding air. It does this very efficiently, but may make colorations in an objectionable way.
This is why I wrote what I did, because it is truly the listener's decision if the trade-offs are worthwhile in each individual case.