While this game isn't very expansive and doesn't directly tie into the Mega Man timeline, it still contains the quality that Capcom has always given its games! I'm sure there's a way to link it to the other series timeline though. Maybe there's something Capcom hasn't told us yet. Still, they managed to take a spinoff and turn it into a full fledged series!
First off, the ruin designs are excellent - maybe even better than the 1st game's - but not likely. A couple of the key mazes in this game involve backtracking to the same place well more than once, which can get tedious, especially when the area is filled with water or the gravity is heavy or whatnot, and it slows you down. Other than that, the mazes are flawless!
There is a slight problem with the battles though, and I'm sure those of you that have played the game have seen it - the 'Ultimate Technique' of locking onto the prime target and blasting away while running in a constant circle. It makes many battles way too easy.
The graphics have been improved from the last game. The models have higher polygons counts and much better coloration (something the last gamewas really lacking). The music is much better too, and not quite as downright corny as the 1st game.
The plot goes into more depth, too. It's very slightly on the darker and more serious side, and the characters are cooler too (Sera is the most unusual villain I've ever seen, but she's devoid of any and all emotion, and definitely the perfect villain for this story. What makes it better is that you don't see it in her until it's too late). The plot explains more of Mega Man Trigger's origins and even the reason why he's on the planet - I won't reveal that though). The game definitely has its lighthearted moments. The Bonnes are still there, which is a definite plus! There are some new pirates too.
All things said (and I could ramble on longer about how much I like this game), the game is definitely worth getting if you're either a Mega Man fan, or if you played the first game and then left in the dark on what the hell was going on. It gives plenty of opportunities for free exploration, and you always find something the second time around you missed the first time (whether it's in a town or a ruin, I gurantee there's gonna be something new to see).