I've been using latest beta in past few days and IDE has stability issues in designer mode.
Basically I've been creating simple UI, few forms with several controls, so I'm placing controls on form, changing their properties, position, text, assigning events etc and it crashes every couple of minutes.
Usually it happens on mouse clicks, selecting different form/unit or different control in object inspector. I've sent several bug reports so hopefully that will help you fix it.
There is also problems with simple selection of existing controls, I select one label, then edit and when I try to select label again (with mouse) it doesn't work or selects label parent.
Selecting controls from object inspector usually works but sometimes it crashes or doesn't display all controls in list. Unit structure displays all of them but I cannot select control with it, so I think it would be a good feature to allow so.
Assigning events to controls is also problematic, it doesn't crash but it messes up code. For example I've added on MouseEnter/Exit for label control, and sometimes dbl click in ObjectInspector doesn't create event for it or it creates a duplicated event (event with same name already exists, this occured when all links between control and events were lost so I've tried to just add them again in OI).
Assigning all through code seems to work fine, only issue is IDE stability (I've also tried latest official full (not beta) and there is much better, so I think you'll be able to fix all these problems and make it more stable.
Also changing IDE theme, like Amethyst Kamri changes all popup menus captions in IDE and editor to Asian chars so it's unusable.
Other than that you've done a pretty good job but there is much room for improvement, for help for properties of controls, right now I have no idea what most of properties do or what is expected behaviour, browsing source code does help but not always.