I gotta say Oh, Sleeper is pretty rad, but the one thing that puts me off are the vocals. It's just not to my liking, they seem overly forced and maybe even juvenile (does that make sense?). I like the effort they put into their instrumentals, since a big reason I tend to reject metalcore are the simplified riffs and clumsy breakdowns. Oh, Sleeper definitely doesn't falter in that area.
After listening to your 4 songs I can honestly say the band has a certain quality to it, and the lyrics aren't cheesy either, which is a big plus.