This is a very brief summary of changes I've observed after installing the RTM version of Windows Vista Service Pack 1 on my Vista Ultimate x64 machine:

• WCF developers beware: After setup, all WAS listener adapters are shut down and set to disabled. I'm not sure why this happens, but all your WCF services that use TCP, MSMQ, or Named Pipe transports will of course no longer work. Make sure that these services are enabled after installing SP1.
  
  
• WCF and web developers rejoice: IIS Manager now has a lot more functionality than in Vista RTM:
  • Protocols can now be enabled in the GUI. No more appcmd.exe set app "Default Web Site/YourService" /enabledProtocols:http,net.pipe,net.tcp required. You can set these in your application's advanced settings.
    
    
  • HTTP caching headers can now be set in the GUI. Unfortunately, my previous remark of a few implementation shortcomings remains true. The GUI lets you set /clientCache.cacheControlMode:DisableCache, /clientCache.cacheControlMode:UseMaxAge, and /clientCache.cacheControlMode:UseExpires, but not custom strings, so don't forget about appcmd.exe completely.
    
    
  • There's way more—make sure to check out all the new configuration options!