Problem: My company says they are switching to Office 365. Does that mean I have to edit all of my workbooks online?
Strategy: No. When you get Office 365, you get the full version of Excel 2013. It streams to your computer. You are not stuck working in a browser. You can keep saving your workbooks locally on your own computer or company network. Optionally, if you have to work on a file at home, you can securely save it to your OneDrive account and then open the file from home.
The PR people at Microsoft tell this story: Back in the 1930's, people were afraid of banks, so they kept their money under the mattress. If there was a house fire, their savings were lost. Microsoft says that people keeping their files on the local hard drive is a similar situation: if there is a catastrophe, you local hard drive and the backup media are all going to be lost. I am not quite sure I buy the analogy just yet. After all, the FDIC insures my money in the bank. I don't see an FDIC for data yet.
What's In It For Me: You can get new features sooner. For the last decade, Microsoft would release a version of Office every 3 years. All of the teams: Excel, Word, PowerPoint all had to coordinate and release on the same day. It is inefficient. The Excel team might dream up a new feature, code it, and then you have to wait 3 years to get it. With Office 365, you always get the latest bits. There is discussion that Excel 2015 will be the last large release of Excel. After that, it will all me incremental updates.
As one tiny part of Office 365, you do get to use online versions of Word, Excel, and PowerPoint. These are versions of Excel running in a browser. They work great in an emergency (you are visiting grandma and she doesn't have Excel). In fact, the Excel Web App does a few things better than regular Excel. You can create online surveys. You can have 20 co-workers all working in the same spreadsheet at the same time. Read more about these features later.