I am gratefull for the existance of OpenOffice too. I also see it used by quite a lot of people on Windows desktops. Altough I am not an office documents fan, I constantly need to exchange data with people using Microsoft formats, without OOO I would probably have to run a Windows session somehow.
While I find KWord very attractive and speedy, when it comes to doing work OOO is the tool to choose.
Another point is that I don't really need the latest and greatest features. Being functional, with a usable enough interface and bug-free is enough for an office application. Do not forget that in order to be compatible with everyone me and many other people always advise for using the old Word 97/XP format. ODF would just miss too many recipients; also, most Microsoft Office users I know are decent and considering enough not to send latest and greatest Microsoft formats to me. In many use cases, the world is not going to end if we don't use the latest and greatest technology.
I thank Sun for making this software available to us. As I said before, I know many Windows people using OOO. I think some corporate planning and avoiding open-source extremism makes OOO much more succesfull than other OSS projects, from the number of users p.o.v. at least, if not from that of the number of contributors.