I have just come across a blog post about Alfresco on CMS Watch. In his post Alan Pelz-Sharpe writes that Alfresco is more developer friendly, especially when you want to push SharePoint beyond its limits. I agree that it is easy to push MOSS to its limits, and also agree that there are certain hardships you have to face when you develop with MOSS. But I still can not see how a JAVA based product could be a real alternative.
Here is Alan's original post: http://www.cmswatch.com/Trends/1331-Alfresco-as-a-SharePoint-alternative
If you use, or plan to use SharePoint and push it to its limits, you are probably living in the .NET world. In case you wish to write custom functionality, such as webparts, you must be a professional and determined ASP.NET coder. As you probably know, we also work with SharePoint, and all of our developers are from the .NET world. I made a quick poll, and noone in our office would choose a JAVA based CMS as an alternative to SharePoint. Not because they don't like it, but because they love .NET and whatever comes with it, Visual Studio and SQL Server, MSDN, etc.
If I were an experienced .NET developer, I would look for a .NET based SharePoint alternative. Actually, this could be the reason why you are reading the Sense/Net Portal Engine blog now. There are some examples in Nathan Stults' blog. He also covered our site, and keeps his fingers crossed, waiting for the release.
The Freak Parade, a blog by Nathan Stults: http://www.thefreakparade.com/2008/07/content-management-systems-cms-for-the-net-platform/