I've previously had 2 pairs of Wave rider 17, and two pairs of Wave Rider 18. I run about 70-80km per week.
Initially, the fit felt different to the 18s - in particular it felt like a higher heel position. This bedded down after 20km or so. Also, the laces are slightly elasticated - I have to tie them really tight to get a secure fit. That results in lots of excess lace (even with lock-lacing).
I've now run about 150km in them. Really like them. Anyone who has had the 18s will find the 19s very similar, other than the laces.