I completely agree, the new open/save dialog is awful!
Have you tried the most recent 12.1 beta? We made a few changes to improve the usability and performance of the dialog for the beta, as well as for the 12.0 patch. It should function and perform similar to the standard Windows dialog within Vista and higher.
What specifically don't you like, or feel should be improved?
When I have my text size on my monitor set to 125% (the default value) this dialog breaks. See the 'Files of type' drop down list, the 'Open' button, and the icons beside the 'Look in' drop down list. Also, there is a lot of space between the icons in the 'Local' treeview, forcing me to scroll a lot more than I want to. Take a look at the screeshot below.
You're right, Jason! Looks like we forgot about that possibility. I've updated the code for the next 12.1 beta. It should appear correctly now. Thanks for catching this and bringing it to our attention!