I played the demo too, I am a bit dissapointed however that you cannot play as starters from older generations, even without being on the demo. I have always used a Pikachu Charmander squad and I can't find myself buying it. It looks pretty cute but beyond that the gameplay is typically still repetitive.
Yeah, the biggest downside to the game is the lack of playable Pokemon, especially starters.
Out of the 649 pokemon in the Pokemon World (as of Gen5) you can only find/play as 144 in total.
Compare that to
Pokemon Mystery Dungeon: Explorers of Time and Darkness where you could play as 491 Pokemon, out of the 493 Pokemon as of Generation 4. (Only Arceus and Shaymin were left out).
You can however choose a Pikachu as your starting character however.
Other starters/partner Pokemon are; Snivy, Tepig, Oshawott, Axew and Pikachu.
The storyline seemed rather short, IMO.
I've completed the main storyline now, which took 3 or 4 days for me to do. (Not playing constantly, but playing a lot).
Maybe I was just bad at Explorers of Time, but that seemed to take me much longer.
The storyline is rather sad though.
Hate to admit it, but I was rather close to shedding tears at the very final part of the main storyline. (I won't give spoilers).
I still have the post-Main Storyline to complete however.
