I love the concept of having a story sequel to the mainline games in a rom hack. It's like a fully realized fan fiction. Unova still feels fresh to explore because the order you explore the region is completely different, not to mention the landscape changes that have happened because of story.
The difficultly was just right for me. It takes into account that anyone playing this has likely played dozens of Pokemon games, but it's not so hard that you get frustrated. It just took me two or three tries on each gym.
Really the only negative aspect of the game is that it's made in Crystal. There's some updates, like Physical/Special split, reusable TMs, and Fairy type, but there's no Abilities, Natures, Double Battles, etc. If all else was the same but it was made in Pokemon Essentials for some modern updates, better graphics, and better post game then it would be one of my favorite rom hacks ever. As it stands though it's still worth playing for any Unova fan.