Expression still seems buggy to me. I've encountered a number of destructive issues that have left me re-doing hours of work.
Undo frequently undoes more than just the last action, which can often mean hours of lost work. Sometimes you're lucky and redo works, most of the time I'm not! What's worse though is that even if you can redo on the page you're working on, the last undo you did may very well have removed any recent styles you've made in a style sheet that isn't even open. So there's no way to redo the styles. You just have to remember what you did and recreate them hoping that you get the names exactly right. I don't want to think about how many of my pages have probably been trashed since I've been using it. I guess I'll find out when I test the whole thing.
Another thing that's driving me crazy is the breaking links. The code around links is randomly shuffling or losing chunks, which naturally causes some pretty weird stuff. You can dive in and hand code the fixes but when you're done and you save it just goes and does it again to another link somewhere else on the page. My worst offending page is quite long and has a large number of links so i don't know if there is a limit to what it can handle or something. Either way it doesn't fill me with joy everytime I have to tweak a page, since it might break more than it fixes!
I'm praying there will be an update for Expression soon, otherwise I may lose my loyalty. I've used Frontpage for years and the transition to Expression has been rough. Fingers crossed for a patch!