This is probably one of the few times that I'm wishing that I had Microsoft Office on my computer. (As it happens, as I go to the library for at least an hour every weekday anyway, I just used Microsoft Office there.) Why?
Well, for my latest chemistry problem set, I need to plot a range of data and add a trend line. Although OpenOffice.org Calc can do this, there aren't as many options. It only gives options for linear, exponential, power, and logarithmic trend lines, none of which are what I want. Although the power regression fits well, what I want is a quadratic regression, and this is something that I just can't do in OpenOffice.org, which is really a shame. I remember when testing some distribution that included Gnumeric (I don't remember which one), I needed to do a similar thing then, so I tried to do it in Gnumeric; if I remember right, Gnumeric did offer the option of a polynomial regression line (with the order of the polynomial specified by the user). Score 1 for Gnumeric, 0 for OpenOffice.org. Also, last year, I needed to make a 3D plot (x, y, f(x, y)), which is possible in Microsoft Office Excel. OpenOffice.org, unfortunately, doesn't have this capability, and at that time (I don't know if the situation has changed much now), it couldn't even render an already-created chart properly. I tried to recreate the same chart with Gnumeric, and, lo and behold, it worked perfectly! Score 2 for Gnumeric, 0 for OpenOffice.org.
Also, last year, I found myself needing to create and view many spreadsheets with lots of data (thousands of rows). Although this wasn't problematic per se in OpenOffice.org, it was certainly a lot slower than in Microsoft Office Excel. Score -1 for OpenOffice.org? Maybe.
So what does KPresenter have to do with all this? Well, it's just that in my experience, KPresenter does a whole lot better in terms of usability and ability to create high-quality presentations than either OpenOffice.org Impress or Microsoft Office Powerpoint. That's because the whole KOffice suite is geared towards desktop publishing as opposed to traditional document creation. Score 1 for KOffice, 0 for both OpenOffice.org and Microsoft Office.
Oracle is being rather wishy-washy about the future of OpenOffice.org, which isn't confidence-inspiring either. I would say the only things OpenOffice.org have going for it are Writer and Math. In the near (or not-so-near, I don't know) future, I may supplant Calc and Impress with Gnumeric and KPresenter. And honestly, AbiWord is a pretty good alternative to Writer as well.