Played it till the first boss, and here's the results:
1. The level design is 100% new, and nothing resembles the original game's, which's ok for the novelty, but I also wanted to see the classic ones refurbished just for the kicks.
2. Watch out for the gray spikes protruding from the ground! look like innocuous ornaments but will kill ya before you notice them.
3. You can't jump+fire as fast as you could in the original game.
4. You die and you always start form the very beginning, but at least you don't run out of continues.
5. You can't kill the walking eyeball things with the projectiles.
6. It takes like 6 levels to reach the first boss, the boss is not in a Castle and it's no an insect anymore...
7. You can take as much damage from enemies as gems you have collected, which can of brings some balance to the overall increased difficulty of the new levels.
8. You get a password at the end of the level so you can warp directly into it anytime, which's only useful for giving it to other people because you can continue where you left by just pressing the "Continue" option when you start the game.
9. Giana is now looking for her sister mario-style...
10. The completely nonsensical age discrepancy between the Giana portrayed in the intro and the Giana as a playable character is still there.
11. Music and artwork are ok, but nothing to die for.
12. In order to be able to hit the boss hiding under the ruins, you must first kill the summoned owls, but as it turns out, sometimes the owls will land on platforms which are unreachable without the boss to bounce on (because he's still hiding), which results in the player never being able to kill the bastard.
13. Beat the level and you'll see Giana smiling and making a hand gesture that really resembles a black-and-white comic of a boy some EAB member has for avatar.
14. Can't tell much about the missing items, powers, etc. etc because I was too pissed to retry the boss fight and see what else was this game had to offer, but I think I will when frustration wears off a bit