For a current project the customer needed an Interactive Report with update functionality - in an Excel like style. Since we couldn't wait for APEX 4.0, we decided to build it in the current version.
The requirement is that the user can change some fields in the report (the Expenses, budget and estimates) for every year of the project life cycle and then the funding should be calculated according a defined formula (to financially smooth things out).
So I created a nice view with a formula to show the budget en estimate and the calculate the funding and created an Interactive Report on top of it.
The editable fields are created using the apex_item.text function with the p_attributes parameter set to:
'onclick=editField(<type>,<key1>,<key2>) readonly class="editField"'.
Once the user clicks on the field, the field is presented in a different style, made editable and with two little icons next to it.
After making the change, the user hits the green tick and an Application Process is fired to update the value in the database - and the report is requeried (showing the updated amounts for the fundings). If he hits the little red cross the edit is canceled; the same happens when he clicks another field.
You can see the result here. You can edit the blueish fields and, once you hit the green tick, the fundings for that year are automagically recalculated. I guess even Websheets doesn't do that...
If you are interested in the details of the code, just take a look at the source of the HTML-page!