You'll have no problems - I recently switched, and work in a windows environment - word for mac uses the same format as word for pc, and works fine, better, in fact. iChat / AIM works, but I have had better luck with Sightspeed.com for video chatting with PC friends, mainly because AIM is such a dog on the pc.
CD formats are the same. In practice, you will be able to read and write any removable media you find on a pc. You won't regret the switch, just not doing it sooner!