I am currently in flight school at Fort Rucker, and are in class with many High School to Flight School aviators. It is NOT hard to get accepted for this, believe me. Some flight time helps, but is not necessary. The Army needs Warrants right now really bad, and they are taking some people that lets just say wouldn't be the best choice. If you have your head on straight and did well in high school, you have an excellent shot at getting it. It doesn't take long, either. Do get a letter of recommendation if you can from someone in the Army or NG. Yes, it is an official program now. You don't have to seve enlisted first. There is a guy who is 19 and just graduated high school last year and is flying TH-67's with me (he's my stick buddy right now). He'll be flying AH-64's at 20 years old.
Don't let a recruiter BS you. You can do it, but most importantly, find one who knows aviation. Go to an aviation unit and ask if they know a recruiter that can help you. Most recruiters have no clue about flight school or the Warrant program.
Now, if you want to fly part time and pay for college, etc, go guard like I did. The only drawback is they don't have the High School to Flight School program. You have to serve a minimum of 1 year enlisted first. I served 2 years before I got selected. I'll be heading home in about 9 months back to my house, and flying Apaches on the weekend while working and making a good living.
Good luck!