What i can say is, that the game has terrible backtracking. That's my biggest issue so far with the game.
To be more clear, the first thing of backtracking is always returning to the surface or to an oxygen source, so you don't drown. This gets really tiring after the first 5 minutes. Once you have a submarine you don't need to do this anymore, but I just found today the mobile vehicle bay that you need to craft vehicles.
Crafting and the fabricator are the second thing. Since you have only one centralized crafting bench you have to return to it all the time. While you can make more of them, this is not as easy as in Terraria or Minecraft where all you need is alittle bit of wood. In Subnautica you need rare microchips that are made of silver, a very rare ore in this game. Seriously, it's more rare than gold.
Since you cannot build as many as you like, you have to think twice where to build it. Otherwise it makes backtrackign a pain because you have all the time return to a very bad spot. because you want to craft something.
Inventory is the next hing btu this is with any survival game: You ill eventually run out of space for your items. Building storages is easy but the problem is the same as the fabricator, you want a central spot that is easy to reach from any gathering spot, so you don't waste 30 minutes to return to your base.
Another thing is that you might not be able to collect everytjing you need at first visitings. There are mining spots gathered int he world that are more efficient to get ores instead of breaking limestone outcrops. However, you need a mining tool which is of course part of the submarine that you get later at the game. Finding these precious mining spots again can be hard.
Finding and remembering good resource spots is hard in this game.
Most of this will be easier int he later part of the game if you get more and more tools. Submarines for faster travels, beacons for marking important spots and so on.
One evry important thing that helps in the end game:
The cyclops. It's a giantic submarine that acts as mobile base. You can fit it out with stuff just like a normal base, including fabricators. It also can hold a seamoth,w hcih is the tiny submarine that you find first. the cyclops acts as mobile headquarter, it eases up almost any of the backtracking issues with the game since you can simply move the Cyclops to the places you want to explore.
I wanted to drive my little submarine around and I was near the area where the Aurora (the space ship) crashed when suddenly something attacked me. Something large.
Here is a screenshot (in spoilers if people want to make that terrifying experience themselves):
(http://images.akamai.steamusercontent.com/ugc/102852399388355032/0FE2595F846BA23B51B0034DDF97724D879DF66A/?interpolation=lanczos-none&output-format=jpeg&output-quality=95&fit=inside|1024:577&composite-to%3D%2A%2C%2A%7C1024%3A577&background-color=black)
The thing destroyed my submarine in two bites, I could eject first but then died too because the thing didn't want me too flee. Frustrated I reloaded a save game, since I didn't found anything significant. Didn't want to loose my submarine after all. What I'm currently searching now is the Moon Bay which are the docks for your vehicles. You can park, recharge and upgrade your vehicles there and only there. You can still exchange the energy source of your vehicles (however not recharge the depleted power cells) but upgrading vehicles with rmor, torpedos and other stuff requires a Moon Bay. I don't even know where to find it but that's part of the game, just explore wrecks until you find it.