We went partly OpenOffice about a year ago, but we had to do it in a less than optimal way: quickly. Bascially we were way over our MS Office license count and those with the purse strings would not spring to get us compliant. So IT got to inflict OpenOffice upon the company. And I use the word 'inflict' quite deliberately: we had no opportunities for user-training or even a staged rollout. It was, in the end, a good example of how not to do it.
Many people still use OpenOffice. But most of the squeaky wheels eventually got proper licensed copies of MS Office. For many of them, it was a case of that's what they were familiar with and would complain if IT took them out of their comfort zone. OpenOffice is still regarded as what to install if we can't 'afford' an MS Office license for someone. :-/
Wade.