I've had a few months to play with the Phantom 4. I can say with certainty that it is better than the Phantom 3 in almost every way but it costs a good bit more and the Phantom 3 is still one of the greatest drones on the market today, especially at these incredibly low prices.
I've used every DJI Phantom. I was blown away by the Phantom 1 and it was horrible at recording video. It had a stationary mount that you could screw a GoPro into. It didn't have stabilization and the footage was completely unusable but I still thought it was one of the coolest things I'd ever seen. The Phantom 2 came out soon after and had the ability to add a gimbal to your GoPro to get professional looking footage. I traveled around the world with the Phantom 2 and a GoPro for 3 months and I got some amazing footage.
Here's a quick clip of some of the footage I got in Iceland with a GoPro and without any sort of video downlink
The Phantom 3 Pro was the first time I had ever used a video downlink. Now I could look down at an iPad and watch in HD what my drone was seeing. It had an amazing range, incredible clarity, and zero lag. I was once again blown away that I could buy this for less than $1500 (now it's under $1000).
A few months ago the Phantom 4 became available. DJI sent me a test unit and I took it to L.A. and Hawaii as we worked on our next tutorial with Mike Kelley. It's certainly a nice upgrade from the Phantom 3. It's got a new shape, better battery, it's quieter, faster, and it has obstacle avoidance, but it's not mind-blowingly better like previous versions have been.
Obstacle avoidance is probably the most exciting new feature. Surprisingly, I found that I prefer to turn it off. It really slows the drone down and it limits how close I can get to certain things. It also makes launching and landing from your hand more difficult. If you're new to flying, you'll probably love it. If you're a veteran, you won't appreciate the training wheels.
Perhaps the biggest improvements for me are the speed of the drone, which makes it fly better in high winds, and the improved battery performance. Other than that, it's pretty similar to the Phantom 3. Although the camera's lens is supposed to be improved, it's got the same 4k sensor and I can't tell a difference in footage, although I haven't tried to look at similar footage side by side at 100%.
One strange issue I had with my Phantom 4, which is highlighted in the video above, is the drone descends significantly after going forward quickly. I still have not figured out why but I've learned to live with it.
UPDATE: I've just been sent this video:
For me, the Phantom 4 is enough of an upgrade for me to buy one but I'm also the type of person who enjoys getting the latest iPhone every year. I can justify slight improvements because I use these tools for business and I enjoy having the latest and greatest technology. But most people aren't like me. Most people would prefer to get the most bang for their buck. If this is you, you may want to consider the Phantom 3 Professional or the incredibly priced Phantom 3 4k. It's only $600! That's really incredible.
If this is your first time buying a drone, keep in mind that you will probably destroy it. That alone may push you to the cheaper Phantom 3. But, if you want the hottest toy, I mean tool, on the market today, the Phantom 4 will blow you away.