the suggestion from mlass is the quickest and effective. I had the situation where I have multiple numbers for an entry, such as businesss, home and mobile numbers. The SIM method only copies the first entry.
There is more painful way but it should get *all* of the numbers in each phone book entry.
1. From Motorola Phone Tools, export your contacts to file (CSV, or comma separated value).
2. Go to Windows Address Book (wab.exe in 'Run') and import that file.
3. In iTunes, tell it to sync contacts from the Windows Address Book.
Worked for my 180+ contacts, many with multiple numbers.
If you don't have Windows, you could use some other intermediate system that takes CSV (maybe Yahoo or Google contacts?) to get to one of the three imports that iTunes takes.