- Broken Base: It IS a Sonic game, after all.
- The game's graphics; either you think it's well above fan game standards or looks like a sub-par Unity game.
- The refusal to use Modern Sonic's 'boost gameplay' in way, shape, or form. Supporters point out how the game is supposed to be a refinement of the Dreamcast era gameplay. Detractors point out how the game still uses the infamous mach speed sections for levels, which is widely regarded to be a way, way inferior version of the boost games.
- Never Live It Down: While the fangame is still respected in the fandom, Ozcrash's, the former development leader, Creator Breakdown and alleged "illegal acts" that nearly stopped the development and shut down the site, and led to Ozcrash being kicked out when development resumed and nearly erased from the credits won't likely be forgotten.
- Scrappy Mechanic: Mach speed sections make a return. While this time, running into walls or stage props won't kill you, they're still pretty much just as wonky as they were in Sonic the Hedgehog (2006), with even the tiniest movement to the left or right risks sending you flying off the stage.
- That One Boss: The boss in Grand Metropolis is tricky due to requiring you to dodge some rather annoying projectile attacks in an arena comprised only of a thin walkway that requires you to run towards Eggman to evade some of his attacks.
- That One Level: Some of the levels in the base game's lineup can get pretty brutal at times.
- Worst Cave seems to be an intentional version of this, yet the developers continue to keep it in the game. It's one of the dreaded Mach speed levels with the difficulty cranked Up to Eleven due to incredibly precise and thin walkways, unfair obstacle and enemy placement, and platforming that requires godlike reaction times to accomplish. Oh, and the level has a tendency to lag on some computers.
- Metal Harbor is surprisingly difficult for a level placed so early in the lineup. It's rather lengthy, has some pretty precise platforming at parts, and there's a rather nerve-wracking underwater segment about halfway through that's an absolute nightmare for characters like Sonic who have low air timers.
- Sand Ocean is significantly harder than its original appearance. Quicksand outright kills you with no chance to jump out, enemies are often clustered around spike traps and quicksand pits, and the platforms required to traverse said quicksand pits are small and require a degree of precision to pass. There are items and shortcuts to help you... although they're locked behind gates that only open when you have a certain amount of rings. And considering the nature of this level, that's easier said than done.
- Casino Park somehow made the wonky pinball mechanics from the original game ten times more finicky. The stage is significantly shorter than the original to compensate, but still.
- The special stages in this game can get pretty unforgiving due to it running off of the same mechanics as the mach speed sections. Besides that, the loose controls make it incredibly easy to miss rings or hit obstacles, and you can easily fall off of the later stages, which counts as an instant loss. Trial-and-Error Gameplay at its worst. Thankfully, you can retry special stages from the menu as many times as you want instead of having to seek them out in the levels themselves.
YMMV / Sonic World