Necro hype!
I just received an N64-GC adapter from Why, and testing it on legit GC MQ, it feels incredible.
The control stick feels 1:1 to N64, as Runnerguy has stated. I'm very picky about my ESS since I love to HESS and unbuffered angle change, and it feels exactly like good old console
Either the adapter or MQ, however,
feel like they add maybe a frame of input lag. I've done 2 tests for this.
1) Side-by-side N64 and MQ+adapter. I was able to switch the same controller between the systems and unbuffered DoT Skip with 100% consistency on both systems, back-to-back.
2) Melee, to see if I can detect more minute lag. Fox's Nair seems to come out on the same frame as a GC controller, maybe 1 frame later. So there might be slight input lag.
Overall: Even for someone picky about lag (like me), this adapter is perfectly fine. The stick feels 1:1 to N64 on MQ, haven't tried other mappings. Build quality is not a problem. C buttons are mapped entirely to C-Stick, so Melee jumping does not play like 64. Control stick range outside of Zelda is pitiful on every setting. Do not use as a general-use adapter.
Recommendation? If you're playing OoT or MM, BUY BUY BUY. If not, don't bother, get a Raphnet.