Just wanted to report that my experience is the same as 49Kat's:
1. Before the update, sleep/wake appeared to work fine. Occasionally WiFi wouldn't reconnect, but I never encountered a crash.
2. After the update, waking from sleep always fails: the Vox becomes completely unresponsive, requiring a hard reset (hold power button down for 10 seconds or so, let go, then press it once to boot).
3.
monk127's suggestion (set "Wi-Fi sleep policy" to "never"--
more details) works well for me: as long as WiFi is on, waking from sleep always succeeds. If Airplane mode is on, waking from sleep still fails, requiring a hard reset.
If any Kobo developers are following this thread, and you need diagnostic information for debug purposes, let me know.