I have tube amps which I love and I wanted to get rid of my cabinet, because it takes a lot of space, and I wanted more cabinet options. Captor X delivered exactly that.
It's perfect for home use where you have a suitable audio system anyway, so you can just use that with Captor X's cab simulation. Or if you have an USB audio interface hooked to your computer, and you want to listen to or record the sound directly.
But what I find best about Captor X is the actual sound quality. It makes a guitar and amp sound very authentic, in way that you are used to hearing on records. It also makes more obvious the guitar and amp doesn't actually matter that much, but the cabinet and mics used. The reverb on the device sounds also really nice and just realistic.
Using the virtual microphones and cabinets is quite easy, and I really like you can use them and switch presets without an application: Once you have settings down, you can just use them on Captor X as they are stored on it. No computer or mobile app needed after that.
What I didn't find very usable was the Captor X's own dummy load and attenuation with an external cab. It felt just making the sound thin. The "low volume" setting is also way too low. But I don't use this feature anyway, so not a real issue for me. But I would not buy Captor X just for attenuation use. There are plenty of cheaper attenuators around. But for virtually adding and miking a cabinet with an existing tube amp and getting good results, it's damn near perfect.
The front knobs are also quite small, I don't know how practical they would be in live situation like on stage. But for home use, they are alright.
It would be also pretty nice if Captor X included effects like delay in addition to the reverb, but that's hardly a downside. Units having these features cost like twice as much.