First I need to ventilate a bit about setting up the cube.
Out of the box the cube was uncontrollably loose and fast. After watching J Perm's video it was possible to set up, and once you know how, it's very easy to change the spring tension of the cube. But on my cube the springs were also rather noisy. I had to take it apart completely and lube the inside of the spring houses and then it became better, but I do need to run the cube on a looser and faster setting than I prefer to mitigate the problem with the friction on the springs causing noise. I was running the spring tension system on the firmest setting first (8) and now I'm down on 7. I guess that in the long run, I will benefit from learning that as I should be faster once I learn better control. The cube needed lubing as it it was very dry out of the box.

About the cube itself.
I like the ridges and after setup the cube became very nice. I'm still breaking it in but I have high hopes for it. The magnes have a good strength and all in all I'm very happy about it.

My first solve was a pb. I got a 6.825
It is so smooth and lockups rarely happen
It is very fast as well

It comes in a nice magnetized container. Inside, there is the cube, its display stand (which is really high-quality and perfectly sized for the cube), and some tools for the spring mechanism, which is actually really good. I use spring setting seven, and I really like the cube. After a solve on it, you don't notice the ridges anymore.

Out of the box, the cube was very loose, but it has many ways to customize it to make it perfect. I put it on the 8 setting and tightened it a bit. After a few months of breaking in, I enjoy solving on this cube, much more than on any other cube. With a bit of breaking in and setup, this cube could easily become anyone's main

This cube is a perfect gift, but make sure you don’t put in lubicle black because, if it is possible, this cube is too fast so keep that in mind!

I set it up in about 15-20 mins with weight 5 in the core and weight 1 on the pieces. I then watched JPerm's video on this cube to explain the spring compression and tension differences. The next day I got a 8.4 which was my new PB by 0.4 seconds. Great Cube!

This cube fixes all problems with the 2m. The cube feels amazing and Is a worth upgrade from the 2m.

After nearly 2 months of occasional use of the GTS3 M, I find I still prefer the GTS2 M. The magnets seem to be too strong for me and break up my rhythm. I like the tensioning system.

The tensioning doesnt really matter, because you can change it in 5 minutes max, but it was really dry. Overall, its magnets were not as strong as i expected, but its corner cutting and turning were great.

SHIPMENT:
The time it took from my order to the delivery to germany took 19 days (incl. custom).
The support answers your questions in a decent time frame ( mostly 2-3 days ).
Sadly the USPS Shipment information tracker seemed to be a bit glitched...

CUBE:
Cube wasnt damaged. Nothing was missing.
Right out of the box the cube felt kind of dry which isnt really a bad thing
because you are able to lube the cube how you want it to be.
The tension was okay, but the screws were not tight enough (for my turning style).
It was also pretty fast:
U2‘s were easy possible with just turning it once with a little force (still possible after tighter tension.
However overshooting doesnt really happen in my solves).
Honestly I didnt notice the ridges when I did some first turns. While solving it now it doesnt bother me either.
In my opinion the magnets are the perfekt strenght to hold the cube together.

I got the Gts3m about a week ago and I have done about a 1000 solves on it. The gts2m was my main for every event and my all time favorite cube so I was really excited for the 3. However when I got it it was very dry and badly tensioned so I took some time to set it up with weight five and some angstrom lubes. The cube became better but I still can’t find the right elasticity/tensioning combo that really works. Also I don’t like the ridges all that much and not the magnets very strong feel. I still am going to try to use this cube and explore to see if I can make it good but for now it is not my main.