I prefer Open Office Writer to Word because the way that it handles styles and document hierarchy make more sense to me. Also, the document layout seems to be relatively stable; at least I haven't observed many cascading layout catastrophes in Open Office Writer yet (as opposed to Word).
A big downside of Open Office Writer is its inability to embed many file types as figures (for example, you can't embed PDF). Apple's Pages is much better in this regard.
I dont use spreadsheets much, but even my light use brings Apple's Numbers to its knees. Open Office Calc is much better in this regard. However, Open Office's charts looks like crap, and Excel's chart feature is powerful but a pain to use. Numbers' charts are easy to use and quite pretty, but Numbers breaks down in flames for even moderately-sized documents (as in click, click, draw chart, go get coffee, come back in 5min, Numbers still not responding). I now crunch my data in Open Office Calc or Python and render down-sampled graphs with Numbers.
Open Office Impress is terrible. You are pretty much limited to bullet points, images, and ugly transitions. I hate PowerPoint. Keynote is great; there is no way I am ever going back to a presentation package without a "magic move" transition.
I have tried Office 2007 out of curiosity, for me it was less of a transition effort to go to OO than to get used to MSO'07.
For publication quality writing I use Lyx and Latex. Lets me concentrate on the content and not futz with styles, etc.
For basic day to day tasks OO works very well.
If you want to accomplish something more esoteric, you can probably do it(and there might be more than one way), but you will have to look at external help sites, and that might take some time.
Then again, trickier things in MS Office might take some time to learn, as well.
IMO, best is LaTex, but some collaborators, publishers, and customers don't like it. The advantage of LaTex is that you can spend more time writing and less time worrying about styling and formatting.
For home use it's superb - even my computer-illiterate parents are using it exclusively.
Personally, I only use OpenOffice and have no problems.
For most other uses, I just use Google Docs though.