I have just been reading this thread with interest and sorry if this has been said already...
I am a very very new FA with EZY... have only flown for 4 days inc my supernumery and check flight!
Personally, I find it easier to cross the seatbelts, firstly it does look nicer and secondly for my own benefit as i then know what rows I have checked (i tend to randomly miss one half of the row out!).
If an FA really doesn't want to cross seatbelts, although I can't see anyone agreeing it looks better, then thats up to them. Regarding the sick bags etc then I would say it depends on time left before PAX board, but then as said somewhere above then if mags are being replaced then do sick bags at same time. That is certainly what the crew who I have flown with do. Think of it as being a passenger, I would be slightly apprehensive to say the least if I was boarding a/c that looks like the crew didn't give a damn!