* What's the tab order? (Usually whatever order they happened to be created in, which is often wrong after the UI has gone through some changes.)
* Are they really exactly the same size or only almost the same?
* How do they behave when the window is resized?
* Does one button have one of its many properties set slightly differently from the other one? (Have fun inspecting them all and make sure to not accidentally change anything while doing so.)
* Did you just accidentally move one of the buttons one pixel while inspecting things?
I prefer doing the UI in code, so that everything is clearly spelled out and not hidden in some properties panel. In WinForms it works pretty well with TableLayoutPanel.
Petzold wrote about this approach: http://charlespetzold.com/etc/DoesVisualStudioRotTheMind.htm...
There was just something so natural about the way you could quickly throw together a UI and then hook everything up to it.