I activated it today on French Wiktionary, and didn't encountered any issue. I especially like the fact that it's possible to switch from VE and wikicode while keeping a visual rendering is excellent.
I see that models are not yet available in VE mode, but the notification message is clear, well done.
Here are some additional feature I would love: - in wikicode edit mode, option to show the rendering side by side with the wikicode, rather than a top/bottom layout - possibility to switch to "edit section wikicode" while keeping what was typed so far. Not a big deal, as the wikicode can be copied and pasted, but it would be fine to avoid this additional step and the "are you sure you want to leave this page, all changes will be lost?" message.
Have you been through accessibility tests?