There are hundreds of “Me Too” blog posts about this, so I won’t bore you with more of the same. There are, however, two of what I think are very important considerations about Silverlight 2 RC0 that developers need to know about. You can only find out about this stuff if you take the time to RTFM carefully. In this case that would be the info on Scott Guthrie’s blog and possibly on Tim Heuer’s blog as well. Pete Brown also does a great job of covering details, and he writes well. Finally, another smart person to follow would be Mike Snow, who is a Senior Software Design Engineer in Test (SDET) for Visual Web Developer Tools.
1) RC0 is a developer release only. You cannot deploy RC0 applications to the web. They won't work. It's only for test environments where you want to ensure that existing or new applications will work with the final Silverlight 2 release.
To repeat: there is no end-user installable runtime for RC0, only the developer runtime with the developer tools. If you deploy an RC0 application to the web, your users will be greeted with unfriendly install messages taking them to installs for Beta 2, and will make them confused. That's no good for you or for Microsoft.
2) The Blend SP1 update that all the announcements point to is for Blend 2 – the product – NOT the June 2008 Blend Preview. This means if you decide to install all the RC0 bits you’ll either need to be an owner of a licensed copy of the product (through MSDN Subscriber downloads for example) or you’ll need to install the free Trial of Blend 2, and then apply the SP1 update to that. Of course, if you have it, you will also need to uninstall the June 2008 Blend Preview.
3) As with any Release Candidate, spending 30 minutes carefully reading the Release Notes and Breaking Changes Word document can and will save you hours of frustration. R-T-F-M! It’s taken me years to learn to do this, and I still occasionally slip up, but I gotta tell ya this is the best way to save time: Drop everything and Read The Friggin’ Manual First!
One recommendation I’ll make for a lot of developers who want to continue to work with BETA 2 and still be able to work on their code for the eventual Release version is to put these RC0 bits on a VPC image and do all your experimentation there; leaving the BETA 2 stuff on your regular development machine. I’ve got a VPC of Server 2008 on two of my machines. I can do anything I want with it, and if I don’t like what I’ve done or screwed it up, all I have to do is extract the original 7Zip self-extractor of the image from my USB stick and I’m like “it never happened”.
Have fun with Silverlight and remember to practice Safe Development – especially if you’re doing PDD (Pajama Driven Development).