Jensen Harris, from Microsoft, posted an analysis of the top features used in Microsoft Word. The results aren't really that surprising.

The top 5 features (commands) used by MS Word users are:

1. Paste
2. Save
3. Copy
4. Undo
5. Bold

Together, these five commands account for around 32% of the total command use in Word 2003. Paste itself accounts for more than 11% of all commands used, and has more than twice as much usage as the #2 entry on the list, Save.

Paste is also far-and-away the number one command in Excel and PowerPoint, accounting for 15% and 12% of total command use, respectively.

Beyond the top 10 commands or so, however, the curve flattens out considerably.

There's a lesson in there -- focus on what people use the most. Because that's what matters the most.