At Globalspec, we use Sharepoint as a collaboration tool. I have a big issue with it: it doesn't support Firefox. You get the 'down graded' experience. This means all the spiffy features are gone. For example, if you want to use the rich WYSIWYG text editor, you are out of luck. I'm not the only one complaining.
I have the same problem with Firefox using my old Hotmail account. The 'full' version of Hotmail prompts me that my Firefox 3.0 browser is unsupported and that the product may not function correctly.
Perhaps there are more complicated 'platform support considerations', but I am sick of the BS. Firefox has about 20% of the browser market. Microsoft, stop pretending like Firefox users don't exist. Real developers right code that supports rich experiences in all of the modern (post IE6) browsers.
In the meantime, I recommend Confluence as an alternative to Sharepoint's Wiki component. The downside is it doesn't come cheap...