I experience none....
It's not just Helix 2, it's pretty much all launchers/home replacements with the 3d app drawer. Just not worth it to me, but more power to ya if you don't have any lag.
I'm using Helix 2 and have no lag at all. It's very quick and responsive. Although i'll always welcome an upgraded version if Pete comes out with it.
In theory, theory and practice are the same. In practice, they differ.