Okay, a few comments from me on the achievements to start this discussion
I think the game perfectly demonstrates the principle "easy to learn, hard to master"; and that even goes for the achievements.
The Earth/Mars/Venus/Uranus/eden: It's rather easy to clear stages 1-5. I just finished that all today, wasn't any problem at all. You die from time to time, yes, but then because of knowing the placement of the enemies you do a lot better on your next try and usually make it then.
When having finished all those, you'll already have half of the achievement points you can get - pretty fast if you ask me!
Laser Assasin: 95% shotdowns is also quite okay; I didn't manage that in area 5 yet but almost, and for the rest I immediately had it at the start. It helps to just mash the shooting button because that way you can make sure that absolutely no enemy will escape you.
The Forgotten: Local ranking of 1st in lost area is also rather easy. Here you need to have a somewhat different approach than with the Laser Assassin achievement: It's vitally important that you don't mash your shooting button but always try hitting as many enemies at once; that will drastically increase the score. It's not even important that you manage to get all of the enemies; 150k points is enough after all.
That's as much as I got yet. I'm wondering about the "The Rezident" achievement. First, can you just do the playing time anywhere in the game? The "trance" stage (will unlock after you beat the lost area) just doesn't seem to end at all, so you could just keep it running while you're at work if you feel lazy and whoups, you might have your achievement. Can't try it out myself as I have no cable controller to plug in, and the wireless controller just turns itself off after a while.
Also, I'm wondering if you have to get the 100% shot down and support item for this achievement in one go, or if you theoretically could just only do one of them for example, then achieve the other in a second go and then together they'd mark the level as 100% completed and the game would recognize that for the achievement. Input on this would be nice.
One small side note, one hint: I've found it a lot easier to shoot without my thumb collapsing by setting the fire button to RT.