I'm no fan of Flash. Even the name annoys me :-) But I feel that recreating its capabilities using the trio HTML/CSS/JavaScript (isn't there an acronym for these 3 interrelated technologies?) is often non-trivial.
A case in point: I recently added to Sheetnode the feature of editing the spreadsheet fullscreen. While every Flash component has a fullscreen option, I couldn't even find a jQuery component that implements this functionality.