I have an application which requires 3.5 (not SP1.) My understanding is that SP1 is an additive service pack. Therefore, installing SP1 on a machine would not affect my application in any way besides performance. As far as I can tell from the sources listed below, SP1 is mostly about new features, and significant performance improvements were limited to WPF and application cold-boot time.
http://en.wikipedia.org/wiki/.NET_Framework
http://www.microsoft.com/net/WhatsNew.aspx
http://msdn.microsoft.com/en-us/magazine/dd569747.aspx
http://weblogs.asp.net/scottgu/archive/2008/05/12/visual-studio-2008-and-net-framework-3-5-service-pack-1-beta.aspx
My question is this: My application does not use WPF and starting up the application is already relatively fast. Could my clients see performance improvements by installing this service pack? Were there significant performance enhancements to anything besides WPF and time taken for a .NET application to load?
Most of the major performance improvements were in the WPF and the web spaces.
On x86, however, there is one improvement that can have a significant impact – methods which take struct arguments were not candidates for inlining until .NET 3.5 sp1. If you are using custom value types, and passing these into methods by value, you may see some performance improvements in those calls after JIT compilation.