A couple of weeks ago we watched them from behind the castle. I wouldn't have wanted to see it for the 1st time from that vantage point, but it definitely made for a different experience.
From where we were standing--right by the carousel--if you looked towards the castle, you could see the shooting stars. In order to see the other colored fireworks, you had to turn and face the other direction. We were actually right underneath where a lot of the fireworks exploded. When it was over I had several shards of ash on me, and throughout the time you could feel the bits raining down on you. At one point an ember landed on the ground and a CM--who seemed to be working that area expressly for that reason--ran over and stomped on it.
By the end I got pretty good at listening for the lauch sounds and facing the right direction to see the explosion.
It was pretty cool to actually see the fireworks take off from on top of Philharmagic, and the sound was incredible. It was loud and all around.
If you're able to see Wishes more than once on a trip, I'd try it from right behind the castle once just for the experience.
The night after we viewed it from behind the castle we viewed it from the center of main street about 40 yards from the castle itself. I much prefer that view.
Personally, I think that wishes is the #1 attraction in all of Disney. It is superb. I could watch it every night and still get chills. I'm only sad because the 1st 5 times I visited Disney we never went to the show because I had the attitude "eh, I've seen fireworks before." Wishes is so much more than that.