Somebody should really be fired for the implementation of Subversion in DWCS4. Besides releasing old versions of the subversion client library that totally hamstring you from installing other svn clients on your machine, it's completely unstable.
First things first, if you had been using TortoiseSVN prior to the release of CS4, you'll be happy to hear that you will have to completely uninstall it and delete all of your working directories. Then you will need to go to the TSVN site and dig around in the archives to pull down an older copy that works with svn 1.4. Fun.
Next, if you've been using subclipse in eclipse to get svn access, you will most likely want to completely uninstall that as well. Subclipse doesn't really give you an option to choose which version of the svn client you want to run, so you are going to have to hunt down an old copy and make sure you don't update it or you will break your CS4 install. I took this opportunity to switch to subversive once again and I might just stick with that one for a while. It actually has an option to choose which version of the svn client to use. Handy.
Now that you have everything set up the way you need to make svn work with your workstation, you get to check out all of your projects again since they most likely were running version 1.5.
Oh, and once it's working in DW, it occasionally just loses it's mind and can no longer connect reliably to the repository. For example, I can now check out a new project in DW, but the DW site never recognizes that the files exist in the repository. Blue plusses as far as the eye can see and DW takes a solid 5 minutes to refresh the list of files or startup.
The rotten thing is that I had this working fine for a few weeks and now something has changed and it has gotten out of whack again. So now, when I edit a file and try to save it, I get an error message indicating that the Server and project are not accessible! (REPORT request failed on 'blah, blah, blah'. Report of 'blah, blah, blah': Could not read status line: connection was closed by server (blah,blah). Funny thing is, I checked the file out with Dreamweaver.
WHEN ARE WE GOING TO GET A PATCH?! Stuff like this really makes DW a hard sell into my team.