I'd come closer to buying the mug. Beyond how great the images look, I dig the shape. Still a bit pricey, since I can go down to FYE and pick up other superhero mugs for about $4.00 each (on sale, regularly $7.00).
Now, $20 for that GL ornament? No. I know, it has a light and talks... but, no. Might I suggest an alternative?
Take that $20 and buy a bunch of the 6" GL Movie Masters Figures (you can get sets of the first three from BigBadToyStore.com for $6.80 - that's right, $2.27 each), grab an MP3 conversion of Ryan Reynolds saying the oath off of YouTube, string up the figures to hang on the tree and, presto change-o, a Green Lantern tree. Oh, wait, the lights. Okay, fine - put back one of the sets of GLMM's, buy a string of only green lights from Walmart for about six bucks, and THEN presto change-o.
You know... now that I think about it, I bet I could actually make an ornament out of a single GL Movie Master figure with one of those recordable sound buttons and an LED for less than $20. In fact, I'm sure I can - a button with up to 120 seconds of recording time for about $10, the figure (heck, I have a couple of that movie GL figure just sitting around now), and an LED light and power source for less than $3.00.
Of course, if I made this, I'd find a clip from some movie where Ryan Reynolds says, "I'm sorry," and just record that on a loop.