Yes, all the joints are 45 degress, made with a router bit. See below, and my explanation that follows.
1) This is what the ideal joint would look like if you beveled the edge of one of the boards in the joint. It creates a lip on the inside, but that doesn't matter and is really pretty small.
2) This is more realistic to what I actually got, which is a gap because of imperfections in the allignment.
3) No problem, I used wood fill (bondo) and then just rounded off the whole joint with some sandpaper.
Now, to get even more "realistic." I was using 3/4" MDF, and you really can't get a 45 degree chamfer bit for a router that will go all the way through the edge (they're just too big for a handheld router). Instead, I got a lip on the routered board that looks something like the top drawing below. But no problem. First I sanded off the lip on the inside before gluing the two pieces together, and then I used bondo and sandpaper on the outside edge. These imperfections are exagerated in the drawing, and the result was a nice smooth curve.
BTW, the same idea is used where the speaker panel met the small piece where the marquee is, but I didn't chamfer either piece. That left a big gap (as you can see in the Google Sketchup) but that wasn't a problem because nobody sees that part. I just filled it with Bondo and wood glue. The result was great.
I should add that the whole cabinet was built with dado joints, so the OTHER edges of these boards were firmly secured in dado joints. The joint that is pictured above was not that important to the structure. It was mostly cosmetic.
[EDIT] I should also add that most of the gap is actually filled by the wood glue (Titebond III) and only a small bit had to be filled with bondo.