It's 24.3 MP full frame image sensor offers a native ISO range of 100 - 12,800 and extends to 51,200 although nobody would really want to do that since it's quite noisy at that high of an ISO. The camera's continuous shooting ability goes to 6.5 frames per second which isn't the fastest on the market, but reasonable enough for many types of action events.
It's a relatively small camera body and while it is considered an "enthusiast" camera, I'd say a pro can easily use it for professional use. Would I use it for a wedding? Absolutely! Many pros are now buying this camera as both their main camera and also as their backup camera.
You can read all about the camera through the various reviews on the internet, but let me just tell you my impressions:
1. I like the smaller body and lighter weight.
2. The high ISO ability in low light is adequate, but not as good as a Nikon Df or Nikon D4s.
3. The shutter sound is quieter than a Nikon D4s, but not as quiet as a Nikon Df or Nikon D810.
4. It's full frame! You can get shallower depth of field with full frame image sensors and it handles low light better too!
5. The video ability allows for full HD recording at 1920 x 1080 / 60 frames per second... great for slow motion.
6. It is the first full frame camera with a tilting LCD screen.
7. It has built-in WiFi which works great! You can control the camera to take photos remotely with your smart phone or tablet. You can even transfer images in JPG to your device too! It will also take a RAW image amd convert it to a small JPG for upload to Facebook or emailing purposes!
8. The new face detection matrix metering helps get proper exposure if it detects a person's face in the image!
9. The shutter is rated to 150,000 actuations.
There are a lot of features on this camera, but most importantly, the images look great!
If you are looking for a full frame camera, this is one I would highly recommend. While not as high of a resolution as the 36.3 MP on a Nikon D810, it has plenty of resolution for most applications.