>I made tests today, I selected from lots of joined tables, which are very huge, and issue expression in where clause like:
>('A' $ Amenities or 'B'$ Amenities etc.) - it took 164 sec.
>(at('A',Amenities)>0 or at('B',Amenities)>0 etc.) - it took 202 sec. I haven't index on Amenities.
>So, my conclusion is that $ works faster than at() (at least, if I haven't index). I'm going to change my code appropriately.

Sounds good. I'm not surprised, I think AT() is slightly more complex than $.