A bit more feedback after 17 hours in:
1. I do get why people find Slipstreams annoying, but as Alex stated, just passing them with moving slowly isn't an option (thank god).
It rather seems, that their planned layout ist the problem:
With them running around the core worlds, you often encounter them blocking your path, when you want to travel to the rim or back to the core. For example, I encounted it two times that, while traveling from the core to the south, there were two slipstreams running parallel from east to west (or the other way). Don't think that's ideal.
(On the other hand, if I want to travel from east to west within the core worlds, I stay within the core and don't encounter them at all.)
So adding a bit more variety here, with more slipstreams running inwards and outwards, and maybe even some funnies like spirals, would be an improvement.
2. The reason I'm now making a short break while waiting for the Nexerelin-update is not because of the added 4X-mechanics, but because of another thing mentioned here: The limited number of starting options.
I'm still learning the ships, but right now there are only four different of them to start with in the small start. On the other hand, choosing the quick start or playing the campaign tutorial gives me too many ships with which I don't know and don't understand what to do with.
So adding a random start option with 1 or 2 ships or maybe a faction-start, where you can choose a faction and then get one of their ships, those would be my hopes for the future.