I upgraded to the t6i from an SL1 which I loved but it was just a little to small for my hands. In the past I have owned the T3i and the T3. I have also owned a Panasonic Lumix G3 mft. I find the lenses offered by Canon not only to be of better quality but allot less expensive.
The T6 is definitely an upgrade. The focusing accuracy is excellent and fast. The new 24mp sensor is outstanding and provides detail I never thought possible from the Rebel line. I rarely shoot movies but have tested the T6i and it seems to do fine for my purpose. I choose this over the S because I really didn't see the immediate need for the top screen and I rarely if ever shoot in live view.
The touch screen is a nice added touch and the lcd is of very high quality. The ability to move the screen offers a great tool for those hard to get shots. I guess I will be using live view after all!!
I found the low light capabilities to be vastly improved over the SL1, but those weren't bad either. I tend to use prime lenses and the quality with the new sensor is to say the least phenomenal. You really have to see it to believe it. I show my pics to family and friends on a 65 inch plasma TV. With the new sensor the images are almost 3D. It might be my imagination , but the SL1 seemed to be a dust magnet to me. I have had no such problems with the T6i. They both have the sensor cleaning system but I constantly found myself using it with my SL1.
Build quality seems to be pretty typical of the Rebel line. No creeks and it feels solid in the hand. The penta-mirror viewfinder is what I am used too so I can't really see any difference from other Rebels. I have used it at sporting events and have found it handled perfectly the shots per second is completely adequate. I always wondered why no professionals like myself always make such a big deal out of a few shots difference. Obviously for a pro all bets are off.
In conclusion as an advanced amateur I find this camera to be excellent. It takes beautiful photos like most other Rebels and adds NFC and wireless capability. I did download the app to my phone and took a few remote shots but frankly don't see myself using this allot. It was very simple to pair my phone and worked perfectly, sending pics to my phone and remote use were a breeze. I would love for Canon to add a couple of custom profiles to the selector dial in future rebels, similar to the 70d and others. That would be a great addition in my opinion.
It now sits as #2 in the Rebel line and deservedly so. There is no perfect piece of electronics in the world that is all things to all people. This one fits my needs and wants very closely. It's a great camera in my opinion and should be with me for a few years at the least. I would highly suggest this camera to anyone looking for this specific type of toy. It delivers exactly what it promised, so What's not to like!