Sorry, bad form etc. Forgot to add...

I don't really use PPT, so can't comment on OO's presentation tools.
Spreadsheets, I'm not a heavy-heavy power user - usually because there's
far better ways of doing most of the things heavy-heavy power users of
spreadsheets do... Word processing I do use reasonably heavily, but not
for mailmerge etc.

But - at the end of the day - try 'em both.

OpenOffice is free anyway.
MS Office you can download a 30-day trial.

Install 'em, try 'em, use 'em - see which YOU prefer.