I am introducing wicked_pdf in my app and the generation of the pdf results very very slow. 
When using thin I manage to obtain in many many minutes (more than 10) a pdf with the correct contents, but missing the css and the images.
I now switched to using unicorn with 3 workers, and the request fails after 60 seconds. So the pdf generation doesn't work at all.
here's the output from unicorn:
"***************\"/usr/local/bin/wkhtmltopdf\" -q        \"file:////var/folders/hc/yp8ps4x54rg7clpzf7g6plwm0000gq/T/wicked_pdf20140123-25990-100u2wv.html\" \"/var/folders/hc/yp8ps4x54rg7clpzf7g6plwm0000gq/T/wicked_pdf_generated_file20140123-25990-1hakql5.pdf\" ***************"
E, [2014-01-23T15:45:03.391769 #25693] ERROR -- : worker=0 PID:25990 timeout (61s > 60s), killing
E, [2014-01-23T15:45:03.399291 #25693] ERROR -- : reaped #<Process::Status: pid 25990 SIGKILL (signal 9)> worker=0
I, [2014-01-23T15:45:03.399536 #25693]  INFO -- : worker=0 spawning...
I, [2014-01-23T15:45:03.401747 #26013]  INFO -- : worker=0 spawned pid=26013
I, [2014-01-23T15:45:03.402179 #26013]  INFO -- : Refreshing Gem list
I, [2014-01-23T15:45:06.113099 #26013]  INFO -- : worker=0 ready
my show controller looks like this:
respond_to do |format|
  format.html # show.html.erb
  format.json { render json: @item }
  format.pdf do
    render pdf: "#{current_user.username.dehumanize}_item_#{@item.id}"
  end
end
and I have reduced my show.pdf.haml to: 
%html
  %head
  %body
    #wrapper
      .top_wrapper
        %header.top-header.border
          .container
            .row-fluid.header
              logo
              .span2
                logo2
        .container
          .row-fluid
      .body-wrapper
        .container
          .row
            .span4
              %h4 Comments
          .row
            .span9
      %footer