Here are a list of the gems and what each one will do to the player:
Life Taker :: Take a ball from the players life pool
Give Life :: Add a ball to the players life pool
Speedy Ball :: Increase max speed of the ball movement
Sluggish Ball :: Slow down max speed of the ball movement
Bomb Ball :: A one time hit that will destroy 1 block from each side of the last block that you hit.
Large Paddle :: Increase length of the paddle
Miniture Paddle :: Reduce length of the paddle
Shooter Paddle :: Allows paddle to shoot to assist ball destruction
Bad Blocks :: 3 undestructable blocks appear in the middle of the playing area to deflect your ball. Once you get this, it's not going away. So keep away from it.
Haze :: A thick cloud will envelope over the blocks and will dissapear within 10 seconds. This could suck, so keep away from this one. :)
Challenge mode gems are pretty specific. The reasoning behind a rather large reduction versus gain is because you are more likely to nail the +'s more so than accidently hitting a -.
I am also leaning more to redoing the blocks to match the level you are on. Giving a better 'theme' to the actual level. The gem color will match the theme as well. I decided to keep all of the gems one color to make it less obvious to determine what is good and bad.
Back to work. Take Care,