What version did you upgrade from?

Did you deploy an official release package or did you deploy your own build from source code? If you built from source did you make sure to deploy a release build and make sure <compilation debug="false" in Web.config? A debug build will be slower.

Are you running any custom features?

Are you using .NET 3.5 or .NET 4?

What kind of hosting do you have?

Are you seeing anything in the log under Administation > System Log

For example if you see constant logging of applicaiton start and end events it would usually mean not enough server memory is allocated to the site and that would kill performance.

I'm not aware of anything in the latest version that would degrade performance. Haven't seen that on my sites nor any other reports of it.

Your log is showing very frequent application stop and start events which happens when the app pool reaches the allocated amount of memory usage, IIS shuts down the app then it starts again on the next request but soon/almost immediately reaches it again  thus it just keep recycling the app and that kills performance. If the app had enough memory to keep running it woukld run much faster because application startup entails a lot of JIT compiling by the asp.net runtime.

I would definitely disable the appkeepalive task to see if that helps but the bottom line is that GoDaddy is cheap hosting that doesn't give you much resources in terms of memory. Better hosting would be my primary advice. The keep alive task is meant to keep your app pool from recycling due to low traffic by generating a little traffic to keep it awake and keep IIS from shutting it down due to no traffic (the IIS default is to shut down an app after 20 minutes of no traffic), but your app pool is being constantly shut down anyway so that task is not helping and turning it off may free up a little memory and may help a little.

Best,

Joe