the fermentation should start a little faster since you have a higher initial yeast count. but the overall time probably won't be halved becuase once the yeast get's going, there's going to be so much of it that it'll be going full speed regardless of how much it started with. the start time is probably more important than the overall time anyway, becuase the sooner the yeast gets a foothold in the wort, the less possibility you have of an infection. And as far as the hydrometer goes, don't worry about it. you can use one if you like, but you can brew great beers without it.
"let me be the first to welcome our new insectile overlords"
On deck: Breakfast stout
Secondary: American Pale Ale
Kegged: Imperial red ale, Breakfast stout, Chipotle Irish red ale, Biermuncher's C3C cream ale