[Galaxy Note5 General] BarryH_GEG:
Backwards:

Loss of removable storage

Non-removable battery

Loss of IR blaster

Forward:

Battery - I'll start with why I place the battery here vs. "backwards." Here's a

detailed

review of the impact on battery endurance with the S6 on 7420 with a slightly smaller battery than the S5. Spoiler alert: it's an improvement in the vast majority of use cases.

http://www.anandtech.com/show/9146/the-samsung-galaxy-s6-and-s6-edge-review/3

Many of us AT&T Note 4 owners started getting crappy(ier) battery life after one or more of their updates. I have nowhere to go but up with the Note 5.

The camera - based on the S6 reviews, faster launch times, better low light performance, and now (finally) Samsung's supplementing OIS with s/w image stabilization which many detailed reviewers said was a problem with the S6.

Durability - whoever picked soft metal to create "chamfered edges" on the Note 4 should be shot. I baby my phone and have been annoyed looking at it starting at the three month point (I'm at 12). My Note 4's GG4 display doesn't have a scratch on it after a year without a screen protector. Now the front and back will share that durability. The new metal edges look much less dainty than what's on the Note 4.

Wireless quick charge - enough said.

S Pen enhancements - for those that use it some of the heavier users understand the value of the new benefits. And being able to take notes on the locked device is sheer brilliance.

Samsung Pay - The LoopPay features aren't backwardly compatible with older Samsung phones because of h/w requirements so no soup for you.

Smaller, thinner, lighter, and easier to palm with the curved glass backside edges - enough said.

More powerful - we already know it based on S6 comparisons to both S5 and Note 4. The GPU isn't fabulous but that truly only impacts intense games and those that play them.

Better multitasking - 4GB of RAM with a full 2GB always available. Look at the speed with which recent apps opens, app's launch, and the general smoothness of scrolling in some of the hands-on videos. Faster RAM and NAND are also contributing to this improved user experience.

Better audio - Samsung didn't mention this but it seems both cool and innovative. From GSMArena...

"Another interesting software feature that Samsung demonstrated for audio was UHQA, or Ultra High Quality Audio. I normally don't bother to talk about these features because it's pretty easy for them to end up as gimmicks, but this feature is effectively designed to try and reduce the effects of lossy compression when high frequencies have been cut off. As seen in the photo above, when UHQA was off the sample music topped out at around 8-10 KHz, while with UHQA on we see harmonics extending up to 20 KHz. Subjectively, it did seem that this interpolated version was much closer to a lossless music file, but my ears aren't particularly astute in that regard."

A fingerprint sensor that works and does something - if the Samsung Pay launch goes well, especially with the ability to use traditional terminals, Samsung Pay stands to leap frog the others. Besides, it's cool to pay with your phone and it's amazing how many people are still in awe. I can't wait to start using it at non-NFC equipped terminals. It'll blow their minds.

Memory speed - giving up expandable storage but gaining a 10x faster and more reliable internal alternative is a nice get. And nothing needs to be said about the faster RAM.

Better wireless – check out the Wi-Fi throughput speeds of the S6. Also, the Note 4 had a GPS issue that either affected certain regions (it affected AT&T) or perhaps certain devices. Read up on the S6’s GPS performance. Free at last, free at last.

There may be more but those are the things I remembered and/or meant something to me. Every year, it never fails, previous version Note owners ridicule the just announced newer version and predict the end of the Note-series for things Samsung did and didn't do. They die down after initial sales numbers start coming out and the happy comments from the newer device's owners begin to drown them out. There were 6ish people on the Note 4 forum who were as negative (or more so) than some here. I saw four of them on the Note 4 forum with no mention of their former resistance.

People should buy what makes them happy. ;)