Now we will have ways to get easier and cheaper through the Sector, which is great. But there's also a downside to it, which is this:
Having a fuel efficient, small fleet will be less of an advantage. Likely even fuel guzzling armadas will now be able to travel to the farthest stars, provided the currents are favorable. Which, in my, opinion, is a shame. I love running lean fleets, and even before this change it was rarely worth it for long.
I'll point out if currents are not favorable, they push the fleet in the wrong direction when you cross them or go against them.
Do these just boost the speed if the fleet is moving in the right direction, or do they actively push the fleet (like pulsar beams do)?
They carry the fleet along, so it's more like pulsar beams, though you have a bit more control, and particularly when near the edges. But, for example, if you try to cross one going perpendicular to it, unless you e-burn, you'll likely get carried along for a light-year or two before you get to the other side. If you do e-burn, you'll still get carried some ways downstream, just not as much. And of course this depends on how fast the stream is at that point, too.
So if we're generous and assume any stream going in the the direction in a 90 degree cone is favorable, then there's only a 25% chance any given stream is going to save you time or fuel. There's a 50% chance any stream you encounter is perpendicular to your direction of travel which is likely going to increase your trip by 1 to 2 light years trying to cross it, or you e-burn, which is going to cost fuel and CR. Then there's a 25% chance it's heading in the wrong direction, and you have to run parallel to it but outside it's reach for a good portion, which may or may not force you through deep hyperspace or prevent you taking the shortest route.
So, if you need to do something out of season, or are literally just going there and back in 30 days, my guess this system is probably more likely to make it worse for fuel guzzling armadas, as then you're moving against the flows. It's still an RNG system at it's heart so it is definitely not going to be beneficial 100% of the time. Of course, you can always plan 120 timeout missions with this in mind and do them around the 6 or 12 month mark, or story line missions which never expire, but that's certainly not the majority of the game. In any case, the current story line reward is much better for getting large fleets around efficiently and quickly, and those travel nodes don't disappear on you. For now anyways.
I'm going to need to play the final version of slipstreams first, to get a feel for how much the travel dynamics change before suggesting this will make travel easier or harder on average. I feel like any move to make travel harder at this point is premature as it is unclear, at least to me, that the new slipstream system is easier. On the other hand, the system clearly spices up hyperspace, which is good.