From any page in any language version, the "View Normal Wikitravel" button at the bottom takes you to the Main Page of the English version, making it difficult or impossible to view other language versions on the non-mobile site from a mobile device.
-> Actually, it doesn't necessarily take you to the English version. It takes you to whatever version matches your browser language. This is not how Wikitravel (or any wiki) should work - users should be consciously trusted to choose the language that they want. I have my iOS language (and thus my Safari language) set to German, and it is basically impossible to view the normal version of the English language Wikitravel from my iPhone.
There are no interlanguage links from a given destination page to the corresponding page in another language version.
There are no links anywhere for pages in the sidebar like the Travellers' pub, Help page, or Recent changes.
Recent changes and some other Special pages don't display properly.
Clicking on an edit link on the normal site returns you to the mobile site, making editing almost impossible from a mobile device.