If you're not using the collaborative features of Google Apps, you're not getting your money's worth.
If you're used to Track Changes, we've got Suggested Edits, which allows comments and responses to changes. We also have Comments, which you can tag people in. Did you know you can format font in comments as bold, italics, or strikethrough?
And if the idea of collaboration makes you nervous, check out Revision History. You can flip back and forth between different versions of your document, spreadsheet, or slides.
Finally - want to keep track of changes to your spreadsheet? Notifications are there for you.