After several days with the new client and many hours of continuous usage without crash, 188.8.131.521 crashed on me today.
It happened at the end of my trip. I closed down Flitsnav (an app that warns for speed cams) first, while Waze was still running, like I always do. The menu of Flitsnav, that opens with the bottom right softkey, normally has the normal WinMo layout, like most programs have. Now, the Flitsnav menu had a Waze layout (Waze menu colours, rounder edges like the Waze app menu, slightly different location on screen). Then, when Flitsnav was closed, Waze came up again, but the phone was frozen and Waze didn't respond.
I've seen this behaviour before, also in the older clients like 1.8.0. I've soft reset the device, restarted Waze and sent logs, so I hope the devs can make something from my description.
Still I must say, this client is far more stable than previous ones.