The Samsung Galaxy Note 4 comes running Android 4.4.4 KitKat, the final iteration of the chocolate snack based operating system, but the upgrade to Android Lollipop has now been available for quite a while.
The Lollipop update on the Note 4 provided all of Google's latest sweet treats, including improved lock screen notifications, better Android Wear integration, Smart Lock and slicker performance.
The Note 4 is now benefitting from Android Marshmallow too, which only started rolling out to handsets in June 2016. The update brings with it improvements to Google Now, battery life boosting tools, greater app permission controls and more.
Whether the Galaxy Note 4 gets an upgrade to Android 7 Nougat remains to be seen, but we're not holding out too much hope considering the handset's advancing years.
Of course this wouldn't be a Samsung handset if the Korean firm hadn't done some tinkering with the operating system, and its familiar TouchWiz interface is present on the Note 4.
The good news is that Samsung's 2014 update to TouchWiz is much more refined than previous offerings, with fewer pre-installed bloatware apps and redesigned icons making everything look a lot smarter. The bump to Lollipop has improved on this again, with cleaner icons and less clutter.
Some Android fans will still find it clunky in places, and it doesn't have the same simplistic feel to is as stock Android, but I found it perfectly palatable to use.
The lockscreen of the Galaxy Note 4 gives you the option to launch directly into the camera or the dial pad for an emergency call, plus it can also display information such as the time, date, weather and even how many steps you've taken during the day.
In a similar fashion to HTC's Blinkfeed news aggregation service on its smartphones, Samsung has partnered with flip board to give you easy access to the latest headlines by swipe left to right on the home screen.
Pull down from the top of the screen - which can be tricky when using one hand due to the size of the handset - and you'll access the familiar notification bar.
A selection of quick links are housed across the top, while brightness control and toggles for S Finder and Quick Connect bridge the gap to your notifications.
To help you tackle the big screen nature of the Galaxy Note 4 you can shrink select pre-installed app windows down to make them easier to reach one-handed.
Unfortunately there's no support for third party applications, so you're rather limited to Samsung's suit of apps and extras such as Google Play.
All you need to do is drag down diagonally from the top left corner and the app will pop out of full screen mode and into a smaller form factor.
Tap the grey dot at the top of the window to bring up the menu from where you can minimise the app into a floating bubble on screen - much like Chat Heads from Facebook.
I did find that on several occasions I accidently shrunk the app I was viewing when trying to access the notification bar. Not a huge issue, but it can get frustrating if you do it several times in a row.
When minimised you can move the floating window round screen, resize it, and access the Android interface behind it, giving you an added level of multi-tasking.
As with previous Note devices you can also get two applications side by side on screen and the best way to do this is by holding down the Back key below the screen.
This will bring up a column of apps on the right hand side of the Note 4's display, and from here you can drag two onto the main part of the screen to snap them side by side.
Your choice here is limited to some pre-installed apps such as calculator, camera, contacts and email, but there is some third party support including Facebook and Whatsapp.
It's a simple and effective system, but I question its usefulness on a smartphone - there's a better case to be made for its use on tablets.
Some may find themselves using this all the time, but during my review I very rarely bothered.
The multi-tasking button makes it quick and easy to jump between applications, and the fluid interface of the Galaxy Note 4 means there's little delay jumping from one to another.
Samsung has played with the design of the multi-tasking menu, with a series of stacked cards showing all your currently running applications.
Scrolling through and swiping to close, is a fluid experience, plus there's the option to close all at the bottom of the screen, as well as jump into Task Manager.
Something I did find from continued use with the Samsung Galaxy Note 4 is its rather aggressive vibrate.
While many of the smartphones I've reviewed gently hum on my desk, the Note 4 has a much stronger vibrate function.
That's great if it's in your pocket as you're more likely to notice is, but it did lead to some strange looks in the office when I had it out on my desk.
As I've already alluded to the performance of the Samsung Galaxy Note 4 is impressive, and so it should be considering it's packing a 2.7GHz quad-core processor and 3GB of RAM.
That means Android 4.4.4 KitKat runs very smoothly, and I didn't experience any slow down or lag during operation.
Applications and games loaded quickly, and even with apps opening in the small floating window view there was not noticeable dip in the performance.
I ran the Geekbench 3 test on the Galaxy Note 4, and after several goes round it averaged a score of 3351. That trumps the likes of the HTC One M8 (2951), iPhone 6 Plus (2911) and Samsung Galaxy S5 (2905), and shows just how much power is packed into the Note 4.
The Samsung Galaxy Note 4 is a slick performer and the refined TouchWiz interface and excellent QHD display makes this an enjoyable phone to use day to day.