I think the question was very valid. It's like if you describe "an word processing app, but for now it only integrates pictures in the document. Typing function to come later!" - in the same way a spreadsheet is not software that is used to put pictures and tables. Expectations when you see the word "spreadsheet" is being able to run complex, calculations, and maybe macros to accelerate your workflow. Calling this piece of software "spreadsheet" is an abuse of what spreadsheets have been standing for, for a very long time now.
Wouldn't that be only for power users? I am very good at Excel myself but it's not part of my job to work with it so I'd say most of the time I use Excel as a quick storage for data and not as a calculation sheet. Grid sounds great for almost every case where you would fire up Excel but not actually do any complex calculations. It made me think of this article by Joel Spolsky about Trello (and spreadsheets): http://www.joelonsoftware.com/items/2012/01/06.html
Almost everyone who uses a spreadsheet wants to do basic arithmetic in it, though.
Look at the demo video on the site. There's a list of expenses and dollar costs. But you can't automatically sum them? Anyone familiar with spreadsheets would consider that a pretty fundamental feature.
