I like the direction that you’re going here and can hardly wait
Tabbed Spreadsheet Edit View
Multiple tabs will be a great addition, to help group related fields together. Could I suggest that you be able to lock one or more columns when scrolling horizontally, so that column is always visible.
When you right-click on a column header, you have a menu with /Empty/Paste/Set Value/. How about adding /Hide column/Pack column/ commands to that menu. There’s a button on the top right of the spreadsheet views which lets you pack all columns or toggle checkmarked columns. A command to hide empty columns (columns with no info to display) would be nice there.
Accurate Changes Html Report
A report which details what changes have been made; could this report also be run before pressing the commit/save button so that it shows you what changes will be made?
Create Custom Fields (Pro Only)
I like this idea (does Jaikoz already show you unknown / unsupported tags?) When matching online, will you be able to direct the metadata to different (or multiple) fields? I’m thinking of the different ways Album Artist and Sort Order have been implemented.
Tagger Script (Pro Only)
Will this support if-this-than-that logic? Like if TotalCDs = 1 then CurrentCD= blank?