After some thinking, I'm really not sure how a feel about this addition, to be honest. The main problem, I think, is the fact that there's not much of a reason to take a slipstream path outside of the core more than once. Most of the time, when I go exploring, I haul enough supplies and cargo space to last several months outside of the core, and sweep a large quantity of the outer stars - 15 to 25 percent, generally - in a single exploration trip. And usually, that space has gates nicely distributed throughout the entire thing, so I can hop between the core and the fringe at a moment's notice, so there's no need to traverse long sections of empty hyperspace. This means that the only real use would be to take a slipstream going away from the core to start a trip. Plus, the fact that slipstreams randomize every now and then means that if it does happen to bridge a gap between a gate and a system I want to return to, that would only last a short time, so I may not be taking that lane ever again.
I feel like one solution would be to reshape and split up the core. Cut down on the number of gates, and instead have slipstreams form trade lanes between star clusters. You could even make some areas that aren't so civilized, like the pather controlled planets, exist in out-of-the-way clusters that are unlikely to be bothered. I think it'd make travel in the core more interesting, too - you'd have to work out the order you hit each market in with the direction of slipstreams as a consideration, too.
Overall, neat feature - but it doesn't feel like it'd see as much use as one would like from players.