Congratulations on the choice. You'll find these forums overflowing with information on how to maximize your N900.

Just a word of advice, only go into the extras-testing and extras-devel repos IF YOU ARE ABSOLUTELY SURE of what you're doing.

I'm a total noob when it comes to the phone, so I've stayed away from those repos. This has resulted in my phone being one of the most stable devices I've ever owned.