Publicly, Eucalyptus Systems CEO Marten Mickos says OpenStack and Eucalyptus appeal to different types of users. But if you really push some of the partners within the OpenStack community, they see OpenStack potentially competing with Eucalyptus.
Either way, vendors are starting to hedge their bets and promote both platforms. A prime example: Canonical, promoter of Ubuntu Linux, has been a vocal proponent of Eucalyptus. But in recent months, Canonical has also been making lots of noise about OpenStack.