Is an old argument nick already posted before and still I don't see his fuss.
Basing on his profile, all of his devices are underpowered to run Android in its full power so yeah, ICS and JB would lag.
Second, store demos really don't cut it for me, since they've been left running for the whole day with whoever does whatever to it. Android as a system gets faster over use as it learns your app usage pattern and your demands from it. So a 2 week old Android device should be faster and better than when you first opened it.