Well, for starters, it will be much faster than your 800Mhz laptop.
Not only is it double the speed, the technology makes it much faster. And Celeron M's are really high in cache. I have a Toshiba Celeron M 1.8 Ghz, its pretty fast.
Four hours of battery life is a plus
Don't expect to game on that laptop, it only has 256MB RAM, and 512MB RAM is the total it can handle. Also, the video is nothing special. Overall, its a nice internet surfer or movie player, but not gaming rig.