I’m running 4.4.0RC1.
The RT::Extension::PreviewInSearch does work, in that it displays the ticket when you click on a row.
It displays the ticket above the search results, not below, so I’m guessing something in the (search results) page has changed in 4.4.
I’m not trying to be a pain, just wanted you to know!
(I’m quite sure everyone is far more focused on getting the final release out the door, rather than looking at extensions!)