I've never claimed to be an accomplished Slash player, she's one of the champions I've spent the least amount of time with so far, but how's this after 5 minutes practice?
https://www.youtube.com/watch?v=EupNwFN2G8g
Mostly around 650ups bar struggling up the first step a bit, but on average above her old cap. You can't do super long slides in the same way as before without banking, or a long drop certainly. But she still out accelerates everyone and with skill and practice I think we should see some amazing play.
Sliding while targeting someone on the inside of your turn is definitely harder now, but I did manage to hit 699ups in one circle slide which is something no-other champion can come close to.