Have not tried but I'm using Anker 6440mah battery, works well and indeed double up the usage time.
The back cover is slippery though.

I'm mainly on wifi so my SOT using the ori batt is around 4hrs gaming (candy crush) to 6.5hrs web surfing + stocks.
After changing to double capacity, rather impossible to game all the time so it's mostly around 10hrs+ if run to 0%.
I did not take an SS for the 13 hr 38min max projected SOT when I was all surfing + stocks, truely about 2x compared to the ori battery.
I'm still on kit kat, auto brightness at 0 and this phone is mostly for data.

My norm usage :


Little gaming :

Kitkat is relatively bug free for me, don't really want to take the risk of some less used features breaking
(e.g. USB audio) but not reported due to not many using it.
In terms of UI, it's a trade off, some parts look better but I'm more fond of a darker theme
,easier on my eyes, not concerned about the battery savings.

I'll skip lollipop and upgrade to M if it proves to be as stable as Kitkat.

I thought I'm the only one locally facing this issue
My Note 4 has poor gps accuracy compared to other phones so when there's obstruction,
it looses signal much more easily.

Install an app that shows GPS status, see if it looks like this (first 2 pics taken off XDA, 2nd is Andrewtst's SS, last 2 my SS)

First pic is the one that's ok


or

Andrewtst and my Note 4's GPS, very similar (16m is ~ 52ft), he noted in XDA he tested in a room under pillow,
I made a similiar test.



My old Xperia T under similiar conditions.


From the few pics, it's hard to draw a conclusion to what's wrong with some of Note 4's GPS issue.
It's not like it's unusable if you use most modern navigation software (it'll mask most issues so the end user never
even realise how poor their GPS is till it looses the signal.)

It's revealing if you can use a software that is able to force smart lane detection off, you'll see lane hopping.
Worse when you're trying to tag places.

Different phones have varying degree of accuracy, even if you have a Note 4 with this issue, it's still totally useable for navigation purpose
and might not ever notice it unless you're trying to contribute to some mapping data where it becomes quite unreliable.

My 64GB Sandisk also has problems but I suspect it might have been a counterfeit.
Files sometimes get corrupted and lately can't even be formatted.
When I bought it I was lax, out of convenience, bought it online.

Didn't know viewnet now sells the 128GB Evo, had it ordered from Amazon, still waiting for it.