Hi, I'm attending Teched Europe where we announced the Express Products earlier this week.  Several people here have asked me the difference between MSDE and SQL Server Express.  I thought that that I'd include a quick high level summary here:

 

SQL Server Express 2005

MSDE 2000

DB Engine Features

·         Stored Procedures, Triggers, Views, & Cursors

·         Stored Procedures, Triggers, Views, & Cursors

Tools

·         SQL Express Manager

·         None

Database size

·         4 GB

·         2 GB

Programming

·         CLR + T-SQL

·         T-SQL

Workload support

·         1 CPU, 1 GB RAM

·         Workload Governor

Replication support

·         Transactional & Merge (Subscription only)

·         Full Merge only

Setup/Install

·         GUI, Command line, Silent

·         Command line, Silent

Application XCopy

·         Available

·         Not Available

DTS Runtime

·         Not Available

·         Available

XML Support

·         Native XML

·         Non-native support

You can find more details here: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsse/html/sseoverview.asp

I hope that this helps

Many Thanks,

Corey Thomas, Product Manager SQL Server Express