Woon asked in his comment about the % automation we have with our IDE tests.
Currently, we are at roughly 50% automated in the IDE compared to the total number of active test cases. These tests range from DTE manipulations to actual UI interations the way the user would (drag and drop, button clicking, resizing, ...). One way to get at the UI elements is through MSAA. This works fairly well for standard controls. Custom controls make the story more difficult (which is why we resourt to DTE calls if our test harness can't handle certain controls).
It takes about 2-3 weeks for 15 people to cover all the manual test cases we currently have for the VC IDE. And this doesn't include common shell features that the VS team handles.
Our automation's primary purpose is to give us rapid general status on build drops each day (although our automation is split up between daily and weekly test sets). The automation set does find bugs, but by far the most bugs are found through manual testing of new features. Automation is our 'security blanket' as we can get a breadth of coverage in 24 hrs with a second depth after ~72 hours (looking for regressions from the previous known state) rather than waiting for three weeks (which also uses up the whole team's attention) with manual. Both are vital.