Yeah bro, you've hit the nail on the head.
I've clearly never tried optifine or fastcraft, and I'm just parroting mdiyo...and every other user that has experienced problems with the hack, er, i mean mod. I'm sorry if you're a fan of these mods, but there are problems with them, like it or not.
Rendering issues, crashes, sometimes even degraded performance rather than improved... It's a mixed bag, and I've seen all 3 of the problems, but never all at once. Yes, I realize that
sometimes fixes are implemented that fix problems, but really I'd just rather not deal with any of it, is that so bad? Sometimes the fix takes an age and a half, like during 1.6.4 and optifine. I learned to live without optifine at that point.