Excellent, almost must-have mod with a few caveats that hurt so badly to bring up when I think about how much it kicked ass to experience everything pretty much blind for the first time.
Pros:
1. Incredible production value on weapons, the biome, and structures
2. Fun bosses, killer concepts delivered well upon in progression
3. Items and accessories that feel like they deserve a spot in vanilla in the best sense of the word. Not overpowered, never underpowered, wonderful to use.
Cons:
1. Severe bugs at times, including some documented by other users here, so I know it's not just mod conflicts:
-Laser summon drop from Ceiros occasionally stacks repeating audio in one spot with no discernable reason, making the firing noise burn my eardrums out with stacking soundwaves.
-The Glassweaver inexplicably back in the first area you find him, and the Forge closed. Not a big deal, as I didn't have to re-do anything to get him to move, but it made it quite annoying to re-visit the area.
-Worst of all, and again, documented by other users; Auroracle's Temple failing to spawn at all. I mapped out nearly the entire cave system around the ice biome of my Large world, spending around two real-life hours to do so and trying over and over to follow the hint structures that would send me to an area without another hint structure and retreading my steps... not a fun time.
2. Hardmode Issues
-Weapons drop off, mobs scale up. I can wholly understand the lack of new weaponry, as the mod is still in development, but the new mobs added by Starlight River scale up in health and damage when Hardmode is activated. This is at its worst with the swarming enemies, the Gloom ones and the Soul Nibblers. These two enemies have nearly no drops at all worthwhile and scale in health and still deal a decent chunk of contact damage for the amount that spawn in a "pack." It feels unnecessary.
3. Structures/Biome
-Dozens upon dozens of nearly useless combat/evasion challenges pop up in the world, and require pickaxe power to break. Early-game, this blocked my hellevator, which is a rather minor complaint, but these structures also ought to have some sort of scaling or be far less common to take up so much space.
-The Vitric Desert has nearly zero use except aura farming after you've completed the content there, and it takes up a large swathe of the map. This is especially noticeable in Hardmode, when you are more pressed to re-search space for new ores.


I don't often write "reviews" of mods, but this mod made a fantastic impression on me that got soured a bit by a few things. I say it with my heart that I love this mod and hope that development keeps up, because it was truly something special to fumble through it without checking any wiki or anything! It's just the things that not even knowledge could really save me from that are inherent to the current iteration that make me reticient to pick it up in my next playthrough.