There are many Drupal 7 core issues that are tagged as "Needs usability review". It would be awesome to try and keep an eye on this list and review UI changes that are going in to core/7, with the aim of trying not to degrade Drupal usability further with un-monitored changes, as we usually do in Drupal core. The most important ones to review are the ones that are in the review process, marked RTBC or recently committed.
The reaction I've seen to vertical tabs so far concerns me, in that there are developers who are excited about the UI pattern and want to implement it everywhere, sometimes with disregard to it's UI limitations and assets; such as over-loading it with too many tabs, making it's panes too long, or nesting sets of drawers/vertical-tabs. We saw this happen with collapsible fieldsets a few major drupal versions ago, and this is what lead to terrible UIs like Drupal 5 and 6 node forms, views 1, the old ImageCache UI and AdWords UI.
Actually all of these examples stem from the desire that developers have to put all the options on one page, instead of creating new forms, screens, menu items and local tasks for advanced or more detailed options. Is
hook_menu() really that difficult? Or is there another issue at stake here?