Just wanted to add, when my office computer needed to be rebuilt from the ground up (I run a lot of "tests" on it), I decided to run an experiment. I do have a license for MS Office etc, and had to use the e-mail client since we have big corporate exchange server etc, but did not install word, access, excel, or powerpoint.
I have been using OO as my office suite for 3 or 4 months now, and exchange documents with co-workers all the time etc. So far no-one has noticed that I am doing anything different.
I am not a heavy office user, so my experience may not apply to all, but it has been fun and working for me.
PS one really nice feature (IMHO) about MS office is the clipart system. This is a system that OO has yet to achieve as well. There is however work being done in the open source community in the area of clipart. OO is working on implementing import for Scalable Vector Graphics (SVG) files, and the resources for this open standard are improving and increasing.
Check out this link for clipart resources.
<a href="http://www.openclipart.org" title="Open Clip Art Library">Clip Art</a>
Notice there is a place to request specific images, so the library is continually growing, and providing needed images. All placed in the public domain.