I remember downloading it like 6-7 years back and not liking it over individual emulators. Now though it's so easy to download cores and run so many different emulators under one application. It even has runahead latency reduction which is nifty, not to mention it's huge library of shaders.
Now the only problem I have is I can't find a good site for arcade roms that isn't some shady shit. Vimm's Lair, my usual go to, doesn't host arcade roms sadly.
RetroArch is one of the pieces of software that I am willing to ignore the viewpoints and actions of the lead dev.
For one, they are not the only dev. Two, it's open source, and they are not making money off of it. Three, it's a genuinely great piece of software with features that standalone emulators don't have, like slang shaders, mass cross platform support (and portability of code), various lag reduction techniques, automated native resolution and refresh rate output for CRTs, Freesync for LCDs, Linux DRM (Direct Rendering Manager) support, automatic controller profiles, etc.
If it were proprietary, then yeah, I wouldn't be using it.