Within 2 minutes of someone having a Google Spreadsheet invite at our office, we had put it into use as a key tool in our day-to-day activities.
I've been forced to come to the realisation that spreadsheeets are really much more powerful than I'd ever given them credit for. For a long, long time, I've lamented why people would create spreadsheet-style applications when they could build a simple database and get infinitely more power.
However, what a spreadsheet delivers is ultimate simplicity than serves a wealth of purposes. A few of the guys in my organisation, do everything on spreadsheets and as much as I've tried to disuade that in the past, I now tend to view spreadsheets as a bit of an application prototyping environment.
After all, most database-style tools now allow you to easily import data you may have created with a spreadsheet.
However, the problem with a spreadsheet is if you have multiple people editing the same spreadsheet it can get very messy and thats exactly where the real time update ability on Google Spreadsheet comes to the fore.
As I speak, I've got three guys all working on a company spreadsheet. Any change anyone makes can be seen by all of them as it is made. We've got no issues about version changes, read-only access, data not being saved, it's just pure simplicity. And that's what a spreadsheet is all about.
Real-time updating of communal information is key. Any online application that doesn't have this capability is doomed to fail, in my humble opinion. I've tried to get people using online services like Writely, ZohoSheet, etc and they've all fallen down in this regard and people have given up on them because of this.
So while Google has copped some flack in some quarters of late, with people lamenting it's just another me-too product, I must disagree. It and GMail are the only web-based apps I've seen people take too almost immediately.
I think it will prove to be disruptive. (BTW, EditGrid appears to be another online spreadsheet with real-time updating capabilities).