Actually i find that rather strange, because I tried on my android project (1Ghz Xperia Arc) processor and it did not cause any lagg at all, but I haven't tried it on iOS. Are you deploying it using phonegap, in that case it will cause lagg. I recommend cocoonjs cloud compiling for speed, they really are fast. But I will also look at my codes and see if there're things i could strip down from the tick() method, I might make it faster that way.
Ah, btw I found this blog by ashley extremely helpful
I'm glad you liked my behavior... :> Many-many-many thanks for mentioning the behavior on your tutorial. :)