Yesterday Microsoft has released the Visual Studio 2008 SP1 and the .NET Framework 3.5 SP1 for RTM. You can read all about it here http://msdn.microsoft.com/en-ca/vstudio/products/cc533447.aspx
Before you go and download the SP1 for both, download and install the SP Preparation Tool first, you can download it here http://www.microsoft.com/downloads/details.aspx?familyid=A494B0E0-EB07-4FF1-A21C-A4663E456D9D&displaylang=en. This will remove any hot fixes you may have applied which could prevent the installation of the VS 2008 SP1.
Then download the installer here http://www.microsoft.com/downloads/details.aspx?FamilyId=FBEE1648-7106-44A7-9649-6D9F6D58056E&displaylang=en. This is just the bootstrapper to get the VS 2008 SP1 downloaded after which the installation starts.
You can also download the ISO file here http://www.microsoft.com/downloads/details.aspx?FamilyId=27673C47-B3B5-4C67-BD99-84E525B5CE61&displaylang=en
Please note that the VS 2008 SP1 also include the SP1 for the .NET Framework 3.5 so you don't need to install it separately.
If you need to install the SP1 for .NET Framework 3.5 on a server you can download it here http://www.microsoft.com/downloads/details.aspx?familyid=AB99342F-5D1A-413D-8319-81DA479AB0D7&displaylang=en
I have installed VS 2008 SP1 on my Vista PC without any problems. We'll keep you posted if we encounter any problems.