Well, it can be installed and will run on the N900. But you'll first need to download and install over 2Gig of support files before you even install Open Office.
Then when you finally do get to install Open Office there's a lot of poking about in X-Term to get it running. And even then it will take an eternity to start up.

There is an alternative though. AbiWord is available from the Extras-devel repository, but even that's a bit of a system hog because it hasn't been optified for Maemo as of yet.

I did install it, and it's extremely slow to load, but then it works fine, no lag.

The problem is that its interface is not made for a phone, so you won't have a good experience. I recommend sticking to AbiWord or something, and leave OO for emergencies (unfinished projects, show-off, etc.)