Having played the frigate prologue, here are my early thoughts.
The graphical upgrade over the original game is quite substantial. The polygon count, textures, and additions of things like shaders are a generational leap. The improvement and overall graphical quality fall in line with the Halo 1 remake for the 360. It doesn't measure up to the best of the Switch;s graphics like say the Crysis remastered trilogy, but it doesn't have to with the original's art direction and while running at 1080P/60fps. I really couldn't ask for more for a remaster of a Gamecube game. I know there's a fan remake on PC that makes this version look like an N64 game in comparison, but those visuals were never going to work on the Switch without losing the 1080P/60 aspect, assuming they were even possible to begin with. I do want Prime 4 to look substantially better than this remaster, but for what it is these visuals are more than enough.
FINALLY: Someone put in the effort to recreate Wii FPS pointer controls on the Switch. The Wii controls still have the edge because without a sensor bar the joycons can need to be resynced in a way the Prime games on Wii never needed to be, like how it was with Mario Galaxy. Still, THANK YOU Retro Studios for doing that. It couldn't have been easy to replicate the point functionality with just the gyro. And there's also the standard gyro+ right stick aiming option if you want to control it like other Switch FPS games, the original Gamecube-style controls, and the option to play like like a standard XBox shooter. Combined with the upgraded graphics this is the best official way to play the game.