I think you captured really well Adam's personality. I know in many pictures he poses like that, proud and all. For the drawing, you created good shadows on his face. Also you contoured well the leather fabric, having all the reflections. But one element that bothers the viewers eye: the top right corner, you haven't smudged enough the pencils lines. Also, might be a small disparty for his nose, doesn't seem anatomical correct.
This picture has attitude! You've done an amazing job in bringing out the personality of the person within your drawing. Although the background looks a little rough, it just adds to the character of the drawing. The use of shades within your drawing has been used quite effectively. The eyes are drawn to the face of Adam Lambert because that's where the highest contrast is situated in.
I looked at the link to your other portrait of Lambert, and I must say that there is a huge difference in the quality and impact to the viewer from the two pictures. The main two reasons why this one works effectively and the texta/marker picture doesn't is:
1. We can see the whole head which allows it to sit better on the paper 2. The texta looks chaotic in your other picture and this takes away any effect the picture would have had on the viewer. This could be solved by placing the lines of the texta with the flow of the object or in the direction you want the viewer to look rather then in a bunch of different and possibly random directions.
If there was anything to change or fiddle with in this picture, I'd say you could try just putting the tiniest bit more shadow around the bottom of the nostril on our right hand side as I don't think it's quite sitting right