Test Run: Google Spreadsheet
Google is really serious in making a virtual office by offering a spreadsheet for the web. Now several companies already had offered spreadsheet for the web but I have yet to be impressed by those pioneers. I've used some of them in their earlier incarnations I don't know if they've modified, but it(operations) involves the mouse for navigation, or that you're going to write on a separate toolbox. Kind of awkward.
When Google started randomly invited users to test their app, I was fortunate to be invited. I immedietly write away as if it was excel. And what do you know it does feel, for the most part, an excel application. Here's the initial screen, very spartan but I think effective:

The spreadsheet(in my testing) is COL:A-T and ROWS:1-100, very modest but not show stopper. You can write anytime inside the spreadsheet just like excel, thanks to in-place editing. You can format the cell, enter formula, resize the column just like excel. You can even toggle the CTRL+PAGE(UP)/DWN to switch sheets.

Although I got the occasional cannot connect to server when it's autosaving the spreadsheet to the server, I think to persist the entered data, it was understandable since it's still beta.
It's still a long way off if it's to supplant Excel, which I think isn't what Google's plan, I still think it has it's niche market. I haven't tried the group collaboration of the spreadsheet but I think it's cool for the software able to bring group together.
I'm impressed not by how it's going to turn out, but the way the google heads make applications like this; so responsive and so natural you'll think you're using a desktop application. Web applications have come long long way...