I tried out the new wikitext editor and found it slow and awkward. There is a tab labelled '''Read''', but rather than giving me the expected preview it asks whether I want to leave the page.
I saw in another page that preview is hidden in '''Publish''', which is highly unobvious. Even less obvious is getting back to source editing.
Also, is there a way to get into the old editor without first disabling the beta?