nabla:
1. Triple check is possible. Yet very rare in practice.

2. The rule gets very interesting in combination with rule 1. If you can only put your piece in play with a normal check, the opponent can take it off the board by promoting a pawn! :D
In my region bugchess is nearly always played with the combination of these two rulez!

rabbitoid:
If the opponent has only a king and pawns left, a promoted pawn is simply removed from the board!

Rule (2) comes often into play. Early checkmates with dropped pawns/bishops on f2/f7 can be prevented by blocking the own king. This is no beginners rule but quite an interesting defense possibility. Besides checkmating is often too easy by dropping a queen.