I have/had a good time with Samsung devices the past 3 years (sgs3 and note 10.1-14) but now it's time to move on.
Here's my take and it's a bit long.
We've reached the point where each generational device update cycle is becoming less meaningful. The M7>M8, SGS4>SGS5, and now the N3>N4 are all evolutionary. It's no one's fault, smartphones and tablets perform certain functions and you reach a point where those functions can only be improved/enhanced so far; be it via h/w or s/w. I have a N3 which I gladly upgraded from an N2 for because of the move from 720P>1080P, much improved performance, a better form factor, and Samsung's latest s/w (EG: S Note). Looking at the N4 the QHD display is a waste (over 300ish PPI the human eye can't register additional detail) and it's larger and heavier than the N3 with the same size display. It's more powerful but the display's going to take its toll and truthfully, how powerful does a smartphone need to be? I could care less about a heart rate monitor, a metal surround vs. plastic, and "enhanced S Pen feel." I'd like OIS and the better camera but outside of that there's nothing really compelling.
Some of Samsung's newer app versions are worse than their predecessors. I'll give you an example. AT&T did something to their network that borked S Voice for N3 users. That means if you have a Gear its voice capabilities become useless. With some screwing around with the APN and using the SGS5 version of S Voice folks got it working again. The amount of functionality removed from S Voice in the SGS5 version to make it "cleaner and flatter" is staggering. Driving mode got stripped of half its features and the ability to use "Hi Galaxy" from anywhere in the device was removed. A security update Samsung pushed fixed older S Voice versions and I couldn't wait to go back. So don't assume "new" S Note, My Files, Scrapbook, et. al., are better just because they're "new."
In terms of upgraded s/w Samsung's failure to keep their apps updated across older devices is actually going to start to hurt them. The N3 and N10.1-14 are really close in terms of app compatibility and versioning across Samsung's proprietary apps (EG: S Note, My Files, Scrapbook). I don't want to get a N4 with new and different versions of the same apps I use on my N10.1-14. It would be a pain in the ass to bounce back and forth between them not to mention potential incompatibility (EG: Current S Note being incompatible with earlier versions). If you think about it, the N10.1-14 is Samsung's "last great tablet." The 4.4 s/w is solid as a rock, M-UX is causing performance issues on the Pro's and S' which we avoided, AMOLED sucks on whites battery wise making it a productivity user's nightmare, we have all the stock widgets (EG: Mail, S Planner) which got shoved in to M-UX for those that have it, and S-800/Exynos 5420 is powerful enough to support a 2,560 x 1,600 display.
So my next device isn't going to be a N4. It's going to be a SM-P605M from Brazil so I can use it with AT&T's LTE bands. Samsung will eventually release a N10.1-15. It'll most likely have a 4K display (
http://www.phonearena.com/news/Is-Samsung-going-to-launch-a-4K-tablet-by-the-end-of-2014_id56929 ) which won't provide much improvement (the human eye being the lowest common denominator) but will suck tremendous amounts of battery and tax the enhanced CPU/GPU that it'll come with making it not much faster or even slower than the N10.1-14. If the N10.1-15 is AMOLED it's either going to gain a ton of weight accommodating a bigger battery or end up getting crappy battery life compared to the N10.1-14's LCD display. I'm guessing the N10.1-14 will get Android 5.0 but pretty much keep the current s/w outside the OS. Fine by me. That would be my preference knowing my N3 is never going to see the N4's improvements; the latter most likely being a good thing.
So as someone who rode the upgrade train with every generation of phone or tablet I'm done. If the N10.1-15 turns out to be compelling and and has the same Samsung s/w as the N4 maybe I'll get both. But that's a big maybe and I'm in no rush. For the first time I'm actually happy and comfortable exactly where I am.