After evaluating a number of control suites out there, we've just decided to go with the ComponentArt suite. Sure compared with some of the other suites out there they don't have quite as many controls available, but what struck us was the quality and consistency of their API's, visual appearance, cross browser compatibility and general operation. Also, they just work straight out of the box.
Some control suites seem to go for quantity (Infragistics immediately comes to mind), whereas the ComponentArt guys seem to have gone for quality and have obviously spent the time getting it right - which is refreshing to see. Peter's Date Package still seems to be the best quality and best documented controls though (albeit date input and validation only).
Given the quality of the existing ComponentArt controls, and given how great their new charting control looks, I can only assume that the upcoming grid and datepicker controls are going to be equally as impressive.
Its also good to see AJAX features coming through more extensively in the control suites out there (as reported in these forums earlier, the dart controls look pretty impressive - though not the best licensing options).
I can't wait to see how well ComponentArt's grid works with callbacks (AJAX).