Pros:
-Sonic feels really great to control. While not perfect, TT Games have really shown they understand how to build a 3D Sonic game. Sonic is snappy and responsive for the most part. He jumps higher than any other character seems to (even higher than Wyldstyle's double jump). And the fact they left the loops and level geometry in the Sonic Adventure World completely unscripted is (and I mean this with complete sincerity) revolutionary for 3D Sonic. There literally hasn't been a single official 3D Sonic game that has done that. They basically used the same concept from fan-games like Green Hill Paradise and Sonic Utopia, and were able to fully realise it because they have a budget. You can also take advantage of Sonic's physics in any other world and things can get crazy there.
-Aesthetically, it looks really nice. Very crisp and colourful, and many of the zones in question have never actually been realised in 3D or HD. Sonic himself also has a lot of nice animation touches. Instead of "breaking" when he loses all of his health, he does the classic animation from the Genesis games where he jumps into the foreground and off the screen. When other characters get launched from bounce objects and such, they flail about, but Sonic keeps his composure and does side flips because he's used to it. And when Sonic boards the Tornado, Tails drives it while he stands on the wings.
-The actual story mode level is really cool as well. It does a very good job of mixing fast paced Sonic gameplay with the slower paced, puzzle solving gameplay of LEGO games. The latter is generally saved for zones that were already slower paced in their original games, like Marble Zone and Labyrinth Zone. It also has Sonic 2 style Special Stages, and some fun boss fights.
-The content on offer here, surprisingly, is very comparable to an actual €40 game, making the price feel very justified. The Story Mode level alone took me 2 hours at the least, and I only found one secret in it (and it has a ton). It also has a load of alternate paths and what not. As for the Adventure World, it's very big and I haven't actually explored all of it yet, and I've only gotten about half of the stuff in it. I've played that part for at least 4-5 hours.
-Writing is amazing. So many references, some are obvious, but some are more obscure and hidden away. Highlights include Shadow pulling out a gun and Knuckles tossing it into a rift with a disapproving look (and takes off his big Knuckles glove to do so, using a regular LEGO hand hidden underneath), the entire Marble Zone section with Sonic getting progressively more annoyed with Omochao, Big referencing Sanic (yes, that Sanic), and Sonic's freakout moment when he realises he has to go to Labyrinth Zone for a Chaos Emerald.
Cons:
-The Story Mode level really wasn't built for the game's co-op functionality. Although there is split screen, that makes it very hard to see what's coming for anyone playing as Sonic.
-Both the Sonic level and Adventure World are not built for other characters at all. While they will automatically go faster during loops and such in the Story level, and while there a few little optional puzzles for them, general traversal is sort of relegated to Sonic only. My sister actually got stuck somewhere because a spring refused to launch Gandalf properly. This isn't a huge deal since if you're buying this pack, you're probably looking to play as Sonic anyway. But it's something to keep in mind.
-Sonic's Spin Dash works great, but rolling is weird. It actually functions more as a brake move or a more precise attack. It's not a big deal and not even inherently a bad thing, but as a long time Sonic fan, I always just have that urge to roll down slopes and gain some speed, but it never does that here.
-They unfortunately could not get the original music or a straight remix for any of the songs from the Classic games. They made original compositions that are meant to sound close to the original, but the difference is there, and it's a bit off putting, even though the compositions are fine on their own. Also, even some of the actual licensed music from the Sonic Adventure games isn't available in the jukebox. Some of it is used in weird places too. For example,
"Let's Make It" from Sonic Adventure 2 is only used for a random race challenge in the Sonic Adventure World...but it's an underwater race, so not only is the music muffled out, but you also can't do it with Sonic...even though this song is an arrangement of Sonic's theme from SA2.
-There are some definite bugs here and there. Won't go into detail on each one I discovered. This one speaks for itself though.
Overall, I'm having a lot of fun with this. Legitimately a really good, standalone Sonic experience. And I'm not even near done with it yet. Plus, I still have all of the core LEGO Dimensions game to play, which I can now use Sonic in.