A couple of things I have noticed, some may just be due to the fact that it is in Beta. The first is that the results grid is not editable, I haven't seen a way within the tool to make it so. This is a very handy feature in Enterprise Manager, being able to just pull up a table and edit some values. Apparently we'll have to write update queries for every single thing (a real pain in the nether regions) or adopt some other tool.
Also, in the stored procedure editor the having the checkboxes and what-not at the top is handy, maybe too much so. A lot of people didn't know that you could encrypt stored procedures in 2000, but now it's right there staring you in the face, just check the box. I see a lot of folks scrambling for a way to unencrypt their procs when they realize after the fact that they no longer have access to the source.
SQLExpress looks to be an good option for standalone apps, just wondering if it will match Sybase for security.