Pre-ordered both already! :D The best thing is that our college has "Spring-Break" on March 15-19, which just happens to be the week HGSS comes out, so I'll have an entire week to play! \o/
I've been looking at Pokearth on Serebii just to see how soon I'll be able to catch certain pokemon. Luckily, I can get both Growlithe and Gastly really early, though I'll have to trade Growlithe from Heart Gold, and wait until night for Gastly. Once I have my team EV trained and ready, I'll be blazing through the game!