Good, but not that good.
1. Sega seriously just got lazy with CG Movies. Out of around 50 cut scenes, there was fewer than 10 that rendered and done in the good style, while the other 40 is done with the crappy graphic of the game, not to mention it lags and not running it smoothly. The CG movies I hate.
2. Unlike the other three previous games, this game, there is only one character to choose and use: Shadow. Boring as hell. I was beginning to having the idea of banging the CD when I am on my 10th storyline. The stages are awesome, but playing them with the same character over and over again is just plain annoying. The weapons provide a bit more fun, but after a few while they are also getting boring, as I can just grab a laser gun and start killing people instead of grabbing a big Cannon that has horrible aim.
3. The missions. Way too annoying. Especially most of the hero ones. Playing finding stuff in SA2 with Rouge and Knuckles was already annoying enough, but now you can expect me to run 'through' the stage and find those stuff that you need to find. And if you just miss one, you have to go to the beginning unless you remember where the heck you missed that one Black Creature or Gun Soldier. Not to mention a bit repetitive afterward.
4. Too less of secrets. From what I heard from Enzan, after you beat the Last Story mode, (Which is also truely annoying; I had absolutely not the same fun as the last stage in SA2 or SH, and I was beginning to smashing my controller when my Chaos Spear not even able to hit the guy, even if I aim right.) You simply have to just get all As and get an expert mode, like SH's hard mode. Boring as heck, not to mention again, repetitive after you've play with Shadow for the 71st time.
5. Lags. A lot. Especially loading between the CG movies. I was wasting 10 minutes of my 30 minutes play time just to wait for each cutscenes to load. Not to mention frames were getting crappy if there is too much thing going on.
Overall, I think after this, SEGA should just go back doing their multiplayer 3D games. This is simply just way too boring.