The feel of the Harmony H54 Rocket is definitely pretty unique. It's got a wide sized neck with a good amount of space on it, which could be a good or bad thing depending on your personal preference. I personally found it a pretty easy guitar to play, but I didn't get to mess with it for too long since I wasn't playing on the session and was the assistant engineer. However, the player on the session didn't seem to have much trouble at all getting a killer sound from it!
The sound of the Harmony H54 Rocket is definitely impressive, as this is a great guitar for getting that classic hollow body sound, which is a sound that I adore. It's a bit more versatile however, as you can also get some more raunchy sort of sounds from it that aren't really possible with too many of the other hollow bodies that I've used before. It's not the thickest sounding guitar on account that it has single coils, but that's the kind of sound most people are going to be looking for anyway with a hollow body.
I'm not sure how easy or hard it would be to get your hands on a used Harmony H54 Rocket, but I would think that if you were determined you could get one without too much trouble. I'm a big fan of Harmony hollow body guitars, as I think they made some of the best from this time period, and the H54 Rocket is a great example of this. If you can scoop one of these up for a reasonable price it's definitely worth it as this is a great hollow body guitar.