I JB'd my phone last night to 2.2 and now I am getting some rather noticeable lag. I notice it the most when I use an app after not touching the phone for a while. I also get some when I click the home button to wake the screen from sleep. I'm not too sure why it would be doing this. I have WB installed and I hear that could be the issue. I also heard that it could be installer for some reason. I did restore it after I JB'd...could that be it? Any help is greatly appreciated!
Winterboard does eat some resources and can slow things down a bit. Also, depending on the jailbreak method used....a little lag is pretty much normal.