We have not encountered any major showstopper issues with RadControls and Orcas. Right now the biggest issues seem to be the lack of adding controls to VS2008 toolbox during installation and some glitches with design time support - sometimes design and source view stay out of sync.
If you experienced something else, please send us more details which will help us reproduce the problem(like stack trace and steps to reproduce).
All the best,
the Telerik team