TL:DR- Good kit all around, however you may get unlucky with quality control. At this price, it is expected. Buy new pickups ASAP. If you put time (and some more money) into this bass, you will find it to be genuinely fantastic to play.
This kit is an amazing buy, especially for someone who loves putting things together. I recommend you to buy it, especially if you are in Europe (and don't have to pay almost as much as the instrument for shipping). I, however, must list some gripes I have, which I will proceed with below.
To start, I understand that this kit is $85, so I am not mad, just a little disappointed. My main and most significant gripe is to do with the bridge. A single saddle height adjusting screw was extremely tight, leading to it being stripped, removing my ability to adjust it. I have managed to do fine using only half however seeing the saddle all tilted is irksome. My other issue was with one of the tuners being rough however honestly it isn't a big deal as it doesn't effect tuning.
Now, to some smaller gripes. The volume pot is very cheap, and really is more of an on-off switch than a smooth curve. The neck is very wide and thick which makes it heavy, causing significant neck-dive. I find this very annoying but didn't put it in the above section due to the understanding that this is expected on a cheap instrument. I also found the pickups to be extremely underwhelming. Expected at this price point.
Now, to what I have changed to make this bass truly fantastic. I am fortunate enough to have changed pickups on my other p-bass so I had some genuine fender pickups ready for a swap. I am a novice with soldering, however I managed to get everything hooked up. Small note, I soldered the ground wire to the bridge instead of it being loose like the instructions have it. Since the stock pickups don't require a backing to stay together, I had to find some foam laying around to hold my fender ones properly. Other than the pickups, I also added strap locks, and a new bridge from Hipshot to avoid worrying about the botched screw. Lastly, I put in a neck ship to help with getting the action I wanted.
In terms of physical work I have done, I have leveled the frets which also included polishing, along with shaping the headstock. I recommend anyone who does it, gets some nice small files (I managed to mess up my fretboard's edge using a large one). That's why we buy these instruments, though, right?
Another thing, is setup. I nearly completely compressed the spring on the E string with how far I had to adjust for intonation, however the whole instrument was properly intonated within the reach of the stock bridge. Now with my relief and action set right, along with good intonation, my bass feels and sounds amazing to play.
I genuinely love my bass, which I lovingly named rattle-can for how much it buzzed before I did the fretwork. I recommend that anyone with the means to do so, pick one of these up. It is a great time and super rewarding to see it when you are done.