I find that if I'm uploading a lot of stuff that I will get lag trying to do other things. Its only from the gallery and uploading a bunch of pictures though. I'm guessing it has to do with the slower file system which could ultimately be fixed like on the other galaxy s phones.
Otherwise I have zero lag on the device. Just if uploading several pictures at once.
Note 2 (AT&T) and Nexus 10
Treo 650 - PPC 6600 - iPhone 2G - IPhone 3G - HTC Hero - EVO - Palm Pre - Epic 4g - HTC Inspire - Galaxy Nexus - Galaxy S 3