I upgraded to froyo a couple of days back and i've never been happier. It performs better than eclair.
For those having lagging issues, there might be an app hogging all cpu resource. try to find out what that is. Install an app that will allow you to monitor the cpu activity of each running app (e.g. system panel app).
I also have an app which shows me the current cpu activity, so i know when my cpu activity is very intense or its actually doing nothing. I would recommend jkApp. it resides onhe taskbar so u'll always be informed of cpu activity.