Thanks for the help!
As far as the taste goes, I'm not really sure what it is, as I haven't been brewing long and don't have much to go off of besides the descriptions I've seen (cooked corn for DMS, green apple for acetaldehyde, etc.). I'm thinking its DMS, but that may be because that is the problem that I would expect from adding the extract too late and letting it sit, as stated in BCS (thanks for the quote Moby). Also, there is noticeable haze in the beer. When I first pick up a bottle and look at it you can see "clouds" of haze before it gets mixed up by getting moved around.
It sounds like the general consensus is to add the late extract portion at 15 minutes. I am planning on trying again with my next batch, I'll add at 15 min. and see how it turns out. I'm assuming that the impact on hop utilization should be small, as the 15 min. point is still rather late in the boil. How would the higher boil gravity (from the addition of the extra extract) affect flavor/aroma hops?
It should mute them. If you didn't add the extract the beer would be too bitter for the style.
Are you bottling or kegging? If you're bottling, you could be seeing the yeast sediment, which does act like a cloud. When you pour, leave a little beer in the bottle, so the yeast stays in. If you're not bottle conditioning, you might add gelatin to your fermenter a couple of days before you package. That will help clarify your beer.