I have try with other solutions (an HDMI converter/upscaler + a modified AV with S-Video out) and the RAD2x is from far the best solution for a LCD TV, specially if you have a RGB N64. The antialiasing switch is perfect for a 3D games and I have plugged on all the time.
The only bad thing is that it is very difficult to get one...
I made a review in my Youtube channel: https://www.youtube.com/watch?v=yrh2TcYUM58

This cable is all you need, if you want to play N64 on modern flatscreen TVs, even if it has a 4K resolution. It is fast and has an incredible clear picture even with composite cable (regular yellow AV out cable) in composite mode. The colors even mor saturated and more clear if your N64 console exhibit a RGB mode. In this context: The RAD2X is a easy, cost efficient and small solution with a very high picture quality and down to no lag image processing.

This thing is awesome. I couldn't even play my SNES on my monitor with a $20 RCA to HDMI converter, the quality was unbelievably bad. The RAD2X is only twice the price of the cheap converters and the quality is infinitely better. I can finally play my SNES on my monitor and not get motion sickness. The sound is pretty decent on my headphones too. The RAD2X will probably be the best $50 I spend all year.

I heard about the Rad2x after trying a levelhike RGB-toHDMI adapter. I was disappointed with the levelhike due to the interlaced signal it produced. My disappointment ultimately led me to the Rad2x after I learned that it yielded a 480p picture and was compatible with both composite and RGB. The Rad2x was exactly what I had been looking for and produces an absolutely beautiful picture. Highly recommend if you're considering it.

I've had considerable time to put the Nintendo Multi-AV RAD2X through its paces. I've tested it on an AV Famicom (JP, Comp), Nintendo 64 (PAL, RGB and Comp - yes, 2 systems) and GameCube (PAL, for the Game Boy Player, RGB ). All have performed excellently, with fantastic picture and sound quality. I recommend it for all Nintendo Multi-AV systems, except GameCube which you should look for a Digital AV solution. The Nintendo 64 especially, when paired with a de-blurring RGB mod, is simply amazing to behold.