Thought you all might like to hear from a self-proclaimed slacker here.
First off, I don't think there's anything wrong with people looking ahead. In fact, I think most of the people who eventually end up specializing are the people who made that decision very early on. If you want to be at the top of your class you need to hit the ground running. It's too late to decide in your third year that you want to be an endodontist if you've already had 2 1/2 yrs of average grades. You have to at least have an idea that you might like to specialize to stay motivated.
If you go around telling everyone you are dead set on some specific specialty you are going to annoy the heck out of your classmates, but that's just social ineptitude, not necessarily premature planning on your part. Just keep it to yourself, OK? People will like you more.
Personally, I am about 98.5% sure that I want to be a general dentist. I have a personality that is always looking for something new. I like the idea of always being able to branch out into completely new areas. Of course specialists are always learning too, but it is just not the same variety that GP can give you. I like dentistry too much to limit myself to a few procedures.
Knowing that I want to do GP lowers my stress level immensely compared to my classmates. I haven't studied earlier than the night before a test this year and then just a few hours. I sit at the front of the class, pay attention, and make sure I understand the concepts. I don't want to cheat myself out of an education, but I'll leave it to the gunners to worry about memorizing every minute detail of the clotting pathway, thank you very much.
Of course every now and then I get the uncomfortable feeling of knowing that I am burning my bridges behind me; especially, when I see some of the published figures for specialty earnings.
But it's still not enough to make me spend the evening reading immunology instead of taking my kids to the park. Surprisingly, my class rank really isn't terrible right now and I could probably make it into the top 15 by April if I really busted my hump, but I just don't want to sacrifice that much.