Hi Sartay,
I have been using [broken link removed] for the past year, mostly the email application. As for the spreadsheet it is quite different to Excel in usage more so than features. It does need getting used to it. what I do now is use Excel and then save the sheet in Google Apps. I then have access to it anywhere and anytime.
I heard the new Google Chrome will have much stronger and better to use office suites. Until then my be advice is use both when it comes to spreadsheet ( and word at that).
Good luck.
TK