Easily the best casual game I've ever played. Hours just fly by when playing this and it's extremely addictive. Every inch of the game from the steady sense of progression, to the memorable sound effects and music, to the way the game celebrates each of your victories like you've just cured cancer, is all designed to keep you hooked and coming back for more. Lets just say it's very effective, and there's some kind of art to that which I can appreciate when it's not done in an exploitative way. Peggle is an innocent but very intelligently designed game... When I close my eyes now I only see pegs, and all music sounds like Beethoven's Ninth.
It's very luck-based though, so don't try this one if you feel the need to master a game, because it will just frustrate you. The "3D Acceleration" option doesn't work anymore on modern PCs, but I have no idea what benefit it has for this fully 2D game.