After installing 0.18.6,4 version of Welkin Suite, I receive error Unrecognized namespace 'apex' and doesn't auto complete in Visualforce
Posted 10 Jun 2015
The issue with unrecognized namespace is known and we have this in our backlog for one of the next releases. However in the meantime you can warnings display in Error List (by just clicking on Warnings sign) and you won't see it.
Regarding autocompletion - apex-specific completion is not yet implemented, while regular HTML and CSS completion should work fine in Visualforce files. If it is not working for you please let me know and we'll start investigating this.
Head of Product
The Welkin Suite
skype id: vladimir.gubanovich