Matt,
I am a big proponent of adjustment layers and layer masks. I think it's great that you posted an in-depth tutorial. In case you're interested, here are a few more points that I've found newbies generally struggle with:
1. It's a misconception that adjustment layers and masking are advanced topics to be learned after you've learned everything else. It's true you can do some fancy things, but all you need to know to get started is that you can use one tool, the paintbrush tool, to paint any adjustment (hue, saturation, brightness, contrast, etc.) onto your image precisely where it is needed and in the amount that is needed in each spot. It is equally simple to undo or modify any edit by painting the mask with the paintbrush tool. So after you learn to make global adjustments, it would not be a bad idea to go directly to adjusment layers. Having one method to do almost all adjustments is nice. The fact that it gives you total control including the ability to undo or modify previous edits is great. Retouching becomes much more like painting than using various tools.
2. When you create an adjustment layer, a layer mask is automatically created for that layer. You can add a layer mask to a standard layer as well. Layer masks do one thing --- they poke holes in the current layer so that the layer below shows through. More precisely, they hide and reveal what is on the layer containing the mask. The hole cutting analogy is a little easier to visualize. Think of layers as sheets of paper in a stack, and masking as cutting holes in a sheet. Painting the mask black = cutting a hole. The analogy is not perfect because painting with grey or reduced opacity black makes the masked area semi-transparent. The point is that it's not complicated. All you are doing is masking, or cutting out part of a layer. If it doesn't sound very useful, keep in mind that masking lets you apply effects in varying amounts to specific spots on an image. You make a global adjustment like increasing the brightness, and then hide and reveal the added brightness where it is needed on the image by painting with the paintbrush tool.
3. The interface for masking in PS is not real good. That puts a lot of people off from the start. Basically, you switch to 'masking mode' and paint on the actual image to edit the mask. You don't see the paint. You see the affects of masking on the image (layer below becomes visible), but you only see the mask itself on the small, black & white mask icon on the layer bar. The way you switch between 'masking mode' and normal image editing mode is to click the icons on the layer bar. A tiny border will appear around the icon that is selected. It's best to create a layer mask and click back and forth between the icons to see how it works. Note that PS won't let you create a layer mask on the bottom layer because poking a hole in the bottom layer makes no sense. The text on the image title bar will change as well indicating the editing mode. However, it is very easy to mistake which mode you're in because there is not a big visual cue when you are editing the mask. Once you get in the habit of clicking the icons on the layer bar to switch modes, it becomes second nature. Too many people are put off initially because it is not obvious how to edit a layer mask or when you are in mask editing mode.
Adjustment layers contain no image data (picture a blue colored transparency on top of your image to make a blue hue adjustment), so when an adjustment layer is selected you are always in 'mask editing' mode. Note that using an adjustment layer to make an adjustment like hue/saturation is identical to running the standard menu command except that a new layer is created with a layer mask that you can paint to apply the adjustment where it is needed.
I hope this is helpful to anyone considering learning adjustment layers and layer masks. Many more illustrated details and advanced topics can be found in the tutorial posted by Matt.
jbf
