Not always a fan of them. Most implementations don't accomplish what they set out to do, and their usage feels on the performative side. Most of them appear to be composite (or god forbid... RF) filters with slapdash scanlines laid over them, and they do little more than hurt the image quality. I prefer my pixels clean in most cases. There are exceptions, like games that make excessive use of dithering, or (the opposite end of the spectrum) games where the artists simply didn't really know what they were doing and just created a lot of pixell-y noise. Composite or RF blurring and bleeding can help in those cases, especially on colour-starved systems. If I have a choice, I usually still prefer the clarity of RGB though. Their cleaner edges makes games easier on my eyes, which helps if you're sensitive to headaches. Especially if it's a game where I'll have to do a bunch of reading.
The thing I find more important, are aspect ratios. Even people who mean well stumble here at times. There's no one-size-fits-all solution here unfortunately. Some games clearly took the stretching to 4:3 in mind when making their assets, while others didn't. You can probably tell pretty quickly which game did or didn't from looking at the circles in those games. If objects that were obviously meant to be round look stretched out, like a sun, moon, wheel, or morph ball, you'll want to fiddle around a bit.