Microsoft has been talking about how much better the user experience with SharePoint 2010 is when using browsers other than Internet Explorer, mainly, Mozilla Firefox. They have been doing a lot of SharePoint demo’s with Firefox to demonstrate this ability and Firefox has been labels as being a level 1 browser for SharePoint 2010.
However, in my use of Firefox, I have found a couple of things so far that still work only when using Internet Explorer.
1. You can’t upload multiple files to a document library from within Firefox. This is due to the fact that for some of these actions. SharePoint 2010 does indeed still use ActiveX controls. In fact, some people don’t even have this option in Internet Explorer according to this post - http://sharepoint4u.wordpress.com/2009/05/07/no-multiple-upload-no-connect-to-outlook/
2. There isn’t the ability to drag and drop to re-arrange web parts on a SharePoint site or to move them between zones. You must move the web parts around by using the setting in the web part properties.
I am actually somewhat surprised by both of these limitations. The first one probably more so than the first, especially considering that when using Microsoft SkyDrive you have the ability to upload multiple files using Firefox. You would think this same type of functionality could exist in SharePoint 2010.
Based on the most recent posts by Microsoft, http://technet.microsoft.com/en-us/library/cc263526%28office.14%29.aspx, it doesn’t look like they have plans on changing any of these limitations. This site contains additional details on these limitations as well as other limitations that exist for various browsers when accessing SharePoint 2010.