What online spreadsheet software do you think is good?

I was not aware that any online spreadsheets even existed. I have just looked at the Zohosheet via the link you provided and the sheet seems quite reasonable. I have used Microsoft Excel for many years and will always be an avid fan of the program due to it's great versatility. The online spreadsheets are rather basic and a poor substitute for a dedicated program, but for anyone not possessing a spreadsheet this appears to be a decent alternative.