I installed the SQL Server 2005 Express Edition yesterday. I've found it very useful and a good replacement for MSDE 2000.
Management Studio Express which comes with it took some getting use to, but I was soon able to configure and use it with easy.
What I like about Management Studio over Enterprise Manager is the query analyzer is built right in.
What I didn't like was no Import/Export Wizard. That's one tool I use on a monthly basis. After a little web search and reading of some message boards, I found out I needed to install the Microsoft SQL Server 2005 Express Edition Toolkit. The I/E Wizard is a separate application, but can easily be linked in with the "External Tools" options under the "Tools" menu. The I/E Wizard is located at C:\Program Files\Microsoft SQL Server\90\DTS\Binn\DTSWizard.exe.
Moving to this new SQL engine was easier than I thought it was going to be. So it looks like I'll be using SQL Server 2005 Express from now on instead of MSDE 2000.