Factorio is that kind of game that either you love it or hate it, nothing in between.
Sincerely, I love it, because of the following:

- The mechanics are fantastic.
- It naturally becomes harder and more fun as you progress.
- The developers are really dedicated, the game hasn't got almost any bugs and they keep the community informed, not like in some other games (*cough* TF2)
- The community is friendly. In my 200+hs arround 60 are multiplayer and I've never seen someone insulting, raiding or just ruining the fun for someone else.
- Can run on mid-low end PCs, so I can use it on my laptop.
- Runs on Linux.

This isn't one of those games where you can learn everything in the first hours, and completing your first game, or any, will take a big amount of time. You can always improve in Factorio, make things better, faster and more efficient, and that is what keeps pulling you in.