Before I could afford my first, I picked up a lot of that stuff. Then I realized I could afford the rifle if I stopped buying the toys.
Having said that.
The detail is really good on some of the pieces. I have the M4/masterkey combo that I always wanted that way. The scale on the 870 is off a little, but the slide and trigger work. The trigger and charging handle work. The dust cover is moveable, and the mag is removable.
For those that are interested Dragon models has an AR-15/M-16 1/35 scale model kit that includes many many variations of the rifle throughout it's history. It is a little dated in that I don't recall it having the M4 series, but it did have the commandos. I believe it was released in the early 90s. The detail is good, and if you're good at painting, it can make for a neat display. Most hobby shops should be able to put it in your hands for less than 10 bux.