I'm not a fan most of the free amp sims on the market, but this is a notable exception. I heard demos of the Marshall Lead 12 amp and was really taken with it (video below). When the L12X was released, I didn't realize it was a copy of the Marshall Lead 12 or else hadn't been exposed to the real one yet. I just tested this plugin and it warmed my heart. It's dry as dirt when you load it, so of course add some room verb if you want to experience it in a room and rival the sound in the real amp demo. But the distortion quality of this amp sim, even on the default setting, impressed me immediately.