I agree 100%... HTML5 UI for Reports is very clunky, slower and not intuitive when Silverlight's is much better.
We actually use the Excel Add-In a lot now, we just build the report's shell in C4C quickly and then do our View/Selection customization in Excel. We find it quite fast and everyone knows how to play with Excel reports quickly.
Since 1402 I believe, the user-experience in the iPad app SAP Customer Insight is also much better with the introduction of dashboards in HTML5 though.
JB.