I love the different types of views (form view being my favorite) for making data easier to understand. One thing I have always wanted from Excel is the ability to view and interact with multiple spreadsheets on one screen. I like to think of it as a canvas view where you can drop sheets in wherever you want to fit your needs. Each sheet is still represented by it’s own tab, but you don’t have to jump from sheet to sheet to see the data and each sheet has it’s own formatting not affected by the others.
Take for example an invoice generating spreadsheet -you have the header data at the top with it’s own type of information and row widths, then the line item details in the mid-section with their own row widths. And then a third set of information at the footer. Each section could be it’s own independent sheet with all it’s own data types, formatting, column widths, etc shared within one view. Formatting changes you make to the top don’t affect the mid-section, nor the bottom. I know you can fake the look and feel of a spreadsheet using merged cells, but it’s time consuming to mess with, and your perfectly formatted merged cells are still affected by formatting changes made up or down the spreadsheet. I’ve wasted alot of my life fussing about the widths of rows because the data needs at the top of my spreadsheet are totally different than the data needs halfway down the page.
Also, by combining this multi-sheet view with the expand/collapse button, one could create sub-sheets within a spreadsheet -the idea where you can expand a record to show relevant data directly beneath it. The subsheet would be it’s own spreadsheet with it’s own fields and row widths, totally independent of the sheet your currently working on, but it’s right there in your field of view. This would be so powerful for creating sophisticated forms. For example, the main sheet would contain all of your header fields, the sub-sheets would would contain your form questions, with their column types and column widths defined totally independent of the main sheet and any other subsheet. Imagine how navigable and much less intimidating a spreadsheet with 50 tabs would be if you had control in this way.
Engineer-types that build monster spreadsheets would love to have this capability. I know this idea will probably go nowhere, but I appreciate anyone that reads it and has felt the same way before. Thanks! 
Spreadsheet.com Roadmap