My beloved Ls and Js have been plenty useful in building up for a double t spin or speed comboing a ton of lines really fast to overwhelm someone. Give L and J a little love!
I don't know why, but I always imagine knights moving forward and then left or right, I always get infuriated for some reason when I see their movement described the other way around.
The J is a pretty valid piece. You get the second most score by triple clears with them. It's those pain in the ass square blocks that can fuck right off.
The Tetris board is 10 x 20, while a chess board is only 8 x 8. Although if you ever place two chess boards next to each other by accident, you'll have to buy another, so be careful.