I've not used it personally but the have heard good things about <a href="http://www.huddle.com/" rel="nofollow">http://www.huddle.com/</a>
What do you want your intranet platform to do?<p>- Collaboration
- Spaces for documents
- Access control
- Used for forms? (surveys, polls etc? )<p>It's easier to suggest if there are more specific requirements.
With 1K employees, no one thing is going to provide best fit for everyone. Work out what the internet is <i>for</i>, and realise that you might end up using multiple systems for different uses, and find ways to use them together. That's a good thing, because it means you don't have a single monolithic companywide dependency.