Hey there everyone
I bought a phantom a few days ago and sure enough, I snapped the boom. I brought it my LHS and they fixed it on the spot. Now, it flies like new (which is fast and hard to control, heh). How? Dental floss, a support, and zap CA. Altogether less than $10 and 10 minutes of time. Here's how it's done:
First, snake the antenna through the broken boom. Then, lightly CA the boom back together along with a small support (I used the plastic "support" piece hobbyzone tacked on, but i'm sure anything small, sized right, and strong may work) covering the split. **MAKE SURE THE REAR WINGS ARE LINED UP AS BEST AS POSSIBLE!** It's ok if the alignment is slightly off, you can fix that with the trim

. oh, and make sure you don't glue the metal steering cables together or to the boom.
once attached, wrap some dental floss around the both sides of the support. Make sure you dont cover the steering cables or their opening.
CA the dental floss to the boom. IT hardens and becomes very strong. Also, a glue accelerator speeds up drying time so you can be out and flying the 'bird asap.
uhDONE.[8D]
Here's some pics: