I'm using the tools from Infragistics since a few months and saw many others. I'm still satisfied with this toolset and miss nothing. Although I'm primarily working with Windows Forms and WPF, I also tried ASP.NET and Silverlight for another project recently. ASP.NET is already very voluminous, may be a bit too much. Silverlight on the other hand has only a few controls so far, but they are very powerful compared to others. I'm really looking forward to the next SL release Infragistics announced, there will be a lot more to come.