I bought a quad of Greyhounds based on that video. Unfortunately, that video is not the best representation of how they sound in the room. In person they're a bit brighter and the mids are more scooped. That's not to say they're bad speakers. I just gravitate towards British voicing and midrange grind. The Greyhound were not quite to my taste for that. To me it neutered the midrange grind on my Marshall-esque type amps.
One application I found the Greyhounds excel at is with Champ & Blackface style amps. The cleans are rich and chimey. Dirty tones were really nice as well. It keeps they typical American voicing you think of with those amps but with that hint of extra midrange to make it interesting. This is where they found their place to stay in my stable. I put them in a pair of standard sized 212's and run my Champ style amp through them.
The Greyhounds have a lot of good qualities if that's the sound you're wanting. First off they're high enough wattage to handle big amps and will retain clarity when pushed to high volumes. Speaking of high volumes they're rated at 101dB so they're loud speakers to begin with. If you're pairing them with another speaker it's something to keep in mind. They can also handle high gain with no problem. Mojotone states they're a blend between American & British voicings. That's a pretty accurate description, but I think they lean closer to the American voicing with hint of extra mids as I mentioned. Overall they are a solid speaker so it's just a matter of if they are to your taste or not.