Long delay before progress bar appears in software item screen

(I'm ambivalent about whether this should be Medium or High. I think the only thing saving it from High importance is that the spastic "In Progress" item in the navigation pane gives the impression that *something* is happening.)

software-center (2.1.20) maverick; urgency=low

  [ Michael Vogt ]
  * softwarecenter/backend/login_sso.py:
    - improve help text now that ubuntu-sso-client is more flexible
      about it (thanks to Naty Bidart) LP: #624097
  * debian/control:
    - tighten dependency of ubuntu-sso-client (for the helptext)
  * softwarecenter/db/update.py, softwarecenter/db/application.py:
    - add X-AppInstall-Description support and extract it from
      software-center-agent to support long descriptions from
      the agent (LP: #625254)
  * softwarecenter/view/pendingview.py:
    - add pulse for pending purchases (LP: #637377)
  * softwarecenter/utils.py:
    - improve logging of the imagedownloader
    - fix where-is-it for kde4 apps (LP: #635684)
  * softwarecenter/distro/Ubuntu.py:
    - fix icon downloading from extras.ubuntu.com and support possible
      country mirrors
  * softwarecenter/view/appdetailsview_gtk.py:
    - show pulse once the install starts (LP: #637377)
    - support "where is it" for non app-install-data if the desktop
      file has the same name as the package name (LP: #637452)
    - fix icon display in "where is it" if Icon=/path/to/file
  * softwarecenter/apt/aptcache.py:
    - add installed_count to the cache
  * softwarecenter/view/appdetailsview_gtk.py:
    - support bullets with " o item" in the description
      (LP: #584147)
  * send version of the package to screenshots.ubuntu.com so that it
    can return the most appropriate image. that is supported by debshoots
    now thanks to Christoph Haas
  * softwarecenter/backend/aptd.py:
    - fix a flickering in the viewswitcher spinenr when purchasing
      a application
    - hide the "buy" button when installing a purchase, fix uneven
      pulsing
  * merged lp:~mmcg069/software-center/small-ui-fix:
    - fix small horizonal line positioning bug.

  [ Gary Lasker ]
  * softwarecenter/view/softwarepane.py:
    - show a more reasonable number for hidden technical items
      in the installed view of "Provided by Ubuntu"
  * softwarecenter/enums.py,
    softwarecenter/utils.py,
    softwarecenter/view/appdetailsview_gtk.py,
    softwarecenter/view/softwarepane.py,
    softwarecenter/view/widgets/imagedialog.py:
    - create an alternative spinner widget that uses an animated gif
      for when gtk.Spinner is not available (LP: #637422)
  * softwarecenter/view/appview.py:
    - fix crash in _on_transaction_finished (LP: #631132)
    - enable show/hide technical items for "Installed Software"
  * softwarecenter/app.py:
    - fix crash in on_menu_edit_activate (LP: #624913)

  [ Kiwinote ]
  * softwarecenter/view/appdetailsview_gtk.py:
    - add basic a11y support for addon items
    - add a11y support for 'where is it'
  * softwarecenter/view/appview.py:
    - set buttons which aren't rendered insensitive (LP: #630521)
    - use a greyed out 'question mark' icon for pkg not found (LP: #635081)
    - for exact pkg not found matches, we don't always have a appname, whoops
  * softwarecenter/view/cat_view.py:
    - set verbose a11y name for the 'all' button for carousels, such that we
      include the section name (LP: #623163)
  * softwarecenter/view/widgets/pathbar_gtk_at...