I don't interact with Sonic.exe-related stuff much – at least, I didn't until recently, though I was there for the subgenre's frankly problematic origins the very first time it got people's attention online – but I see that it has taken on a life of its own with later creators doing something better with the concept. This addon is pretty neat; a decent challenge for someone who's already beating the game with ease and wants a new enemy to bother them. It – that is, X – is disproportionately more threatening in some levels than others, especially ones where the risk of it grabbing you over a bottomless pit is very real even if you've been nailing your stuns up to that point, but in most levels, I'd call this a pretty fair challenge.
Personally, I would love to have an opportunity to fight and defeat the thing directly, but I understand that's not in the spirit of the addon. I can see that being part of a whole separate level pack designed with this mod in mind, with a boss battle at the end, but as things stand, it's fine. I would also love to see it playable, and I hear someone is already working on that; I'll probably download and play that as well, when that addon materializes.
For now, as a novice speedrunner, I'm sufficiently motivated to beat this thing by playing so good, it'll never actually catch me, let alone kill me. lol
Sonic, dead or alive, is mine!