I'm getting a mac notebook and wondering whether to just go with i work or whether it is worth investing in microsoft office for mac. I'll be running leopard and not windows and kinda trying to avoid microsoft as much as possible - but not at the expense of compatability.

If someone sends me a word document then I can open it with the mac word processor while retaining all the formating? Can I then insert comments and / or track changes and export that back to word while retaining all the formatting?

Can I open ppt presentations in keynote while retaining animation features? Can I export keynote to powerpoint while retaining animation features?

Are there additional features in either i-work or microsoft works that makes one a better option than the other?

I've always been a PC user but the move to mac seems to be a good one with the system stability, system security (so nevermind cluttering up the system with zonealarm and stuff to get datamines) and lack of viruses (so no need for virus protection)... Just want to keep it uncluttered so it is FAST to startup and get going with a presentation / lengthy word processing document