I find that although there has been some improvements in maverick, software-center is still quite slow, lagged and unresponsive. Andrew, unfortunately software-center doesn't offer any output in the console when running the following scenarios. You can test these to reproduce the issue:
1) Speed opening deb file
a-Open a .deb file (software-center shows gray window until it can load information) - 26 seconds
b-Open a .deb file (gdebi opens the file quickly) - 2 seconds
2) Speed opening
a-Open software-center - 20 Seconds
b-Open synaptic - 4 seconds
3) Interface unresponsive while installing
a-Select a large number of packages to be installed (all games for example) - software-center is bogged down by dpkg, unresponsive.
b-Select a large number of packages to be installed (all games for example) - synaptic/gnome-app-install interface is not bogged down by dpkg as they REQUIRE user to confirm packages BEFORE being installed, then BLOCKS the interface when installing.
I would recommend that either the interface be blocked when the user is finally ready to confirm packages to install. Otherwise I recommend removing niceness from dpkg so that it doesn't peg the CPU (meaning installation will be slower than with other package management tools). If there is a creative way to have dpkg and software-center both run without this lag, please post your idea here.
c-After selecting a package you may notice a 15 second lag before it is added to the "In progress queue"
5) Slowness in browsing interface
a-After clicking on "More info" interface is non-responsive (try scroll up, scroll down) until thumbnail loads.
b-Scrolling through list of packages causes visual stutter. Clicking on Category bar does not have an immediate effect.
c-Clicking on history beside category bars create a broken path that doesn't bring you anywhere (white page)
Please let me know which of the following tests you can't reproduce. I am able to upload video recordings of these issues should it be required.