I had some time to mess around with the Analouge 3d over Christmas. Played a bunch of Mario Kart, Mario Kart Amped Up, Smash Remix, Magical Tetris Challenge and Majora's Mask. Hacks were played on a Summercart 64. Everything else was original carts. I can't tell the difference between it and an authentic N64 when I'm playing, and I've played a lot of N64 over the years.
I hooked up my original N64 to the same TV using a Retroscaler 2x from Aliexpress to compare. There absolutely are tiny differences when you put them side by side... a brighter red or blue here or a race timer running a fraction of a second faster there, but I'd be extremely skeptical of anyone calming their MFA in film studies allows them to see the difference without putting both consoles directly side by side.
I played through story mode in Magical Tetris Challenge to test input lag and I couldn't perceive any. No issues doing things like wedging blocks into tight spaces at the last possible moment. Now again, if you recorded the Analouge 3D and N64 side by side, record video and step through frame by frame it's totally possible the 3D adds a frame or two of input lag over an actual N64. However, I'd be extremely skeptical of anyone who says they can perceive it with their naked eye.
Youtube videos do not do the CRT filters justice. They are beautiful.
I tried my Space Station Silicon Valley cart because I heard it doesn't work, and it does crash at the at the DMA logo screen if you don't skip it. If you start a new game it crashes when the dog gets killed in the opening cutscene. That game has always been buggy even on original hardware with the expansion pak, so my guess would be there's something buggy happening with the ram.
Overall I'd say it is to N64 as something like the SupaRetroN HD is to the SNES. Not a 100% perfect clone, but close enough that you won't notice without putting them side by side. However, a RetroN clone is ~$100, and while the build quality is higher overall, I do think the 3D is expensive for what it is. I only bought one because I'm really into N64 and have dozens of original carts I've collected since the 90s. If you don't have a bunch of carts lying around you want to use, I struggle to come up with a reason to buy one over something like one of those cheapish Mister Clones on Aliexpress outside of how aesthetically pleasing the Analouge 3D itself is.