Aim looks to be powerful, two stats to attack! However in practice I'm thinking this to be a +2-+7 bonus which, while quite beefy, is mitigated by medium BAB. Given the name of the class, accuracy seems to be the order of the day. That damage boost though... d4s aren't huge, but I'm wary of XdX/level abilities you can deal more than once per round, which is what happens when you hit higher BABs.
Precise Shot... Trackless Step... No AoO for firing in melee, nice nice...
Light Step has a few nice utility powers effectively at will. I can't imagine any situation you'd need multiple Spider Climbs for on a per encounter basis. Likewise Fly, it's effectively Fly at will at 14th. I wonder if the creator is aware... oh, you're the creator. Makes sense. Well, it looks like you can spread it to allies too, which helps consume uses, but still ends up being effectively at will. Fly at will for an entire party? I'll think about it.
Rangefinder, if I read it correctly, means you can literally shoot the moon at a -NI penalty to hit, since you do still have range increments. Then at 16th level you get the amusing epic feat effect where you can somehow shoot an arrow to Alpha Centuri in 6 seconds.
Trick Shot, I'll get back to these. Looks like a series of gimmick powers.
Keen Perception is eventually +10 Perception checks, makes sense.
Practiced Shooter is a good money-saving technique.
Fast Aim, standard action huh? Alright.. Improved Snipe... Darkstalker...
Wis to Stealth. Sometime tells me this class loves Wisdom.
Greater Snipe leads to situation of invisible distant foes pinging away at people, with said people being likely unaware where it's coming from. The sniper's sure to have optimized Stealth (and has Wis to buff it as well) while the same is not certain of opponents. Thematic, maybe not fair.
Hide in plain sight... veteran shooter...
An attack as a move action? What an unusual thing.
Superior Snipe, Mighty Aim...
Attacks as immediate actions, spellcasters shutter in fear at using concentration against base damage + 17d8 every time they cast something at any range.
Fire All gets amusing if you have someone with a well optimized perception or other extrasensory senses (it seems, even scrying) with arrows flying across the universe to smite everyone Majin Buu style.
And level 20 is a save or die.
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My final analysis is that while the class is good (though possibly subject to unintended consequences) it's too strong for this level of game. Its in that uncomfortable area of not being as versatile as your spellcaster, but still being absurdly good with your one trick pony to the point where I find it difficult to find appropriate counters. So sorry, class is denied, but don't think of it as a criticism of your class making. I quite enjoyed it.