Here's the deal. (From another Army combat arms officer-been both enlisted infantry and Armor (tanks) as an officer,11 years total). For making it through basic, the only things that will really undermine you are pushups, situps and the 2 mile run. The minimum standards are all over the web if you search for them. (Look up 2006 Army APFT standards on google.) While you shouldn't shoot for the minimum, that will get you through. You have to be ready to do that minimum-at least- when you are cold, wet, tired and hungry, so that's why being able to do more is better.
Right now I am a commander at one of the Army's basic training centers, in charge of Drill Sergeants, so I can honestly say we see failures of every event come through here. Failing a ruck march time won't get you canned (you may have to redo it, but you will still graduate.) The only things that will hold you in basic if you fail is failing the pushups situps and run.
The best way to improve on pushups and situps? Keep doing them. If you have a friend to help, have him/her assist you when you get to muscle failure. If you don't, do modified PU's by going to your knees. As far as the run goes, interval sprints help a lot. Keep in mind though, 2 miles is more of an endurance event, and you have to mix distance running in too. If there is one event to come prepared for, it is this. In the Army, you will run all the time, (Depending on the unit you are in) and you need to get used to it.
The rest is just discipline. Getting up at 4 AM or not getting to bed at all sucks along with other Army hardships, but it's like preparing for a punch in the jaw. It's hurts no matter what. If your mind keeps focused on the endstate (graduating) you will find that you will be able to make it if you are determined.
You are young right now, IF you want this, then do it. It's something you can be proud of and tell your grandkids about one day. If you don't want to, that's cool too. It's a volunteer Army. If you are interested in a specific school or unit like airborne school or getting into the Ranger Regiment, get it IN YOUR CONTRACT. If your recruiter won't do it, walk away. The Army is always hiring, and that recruiter NEEDS your business. Make him work for it by getting you what you want. They even allow fresh recruits to sign up for the Special Forces training program now. God how I wish I could have done that when I was younger and less broken then I am. If you want that sort of thing, go for it now.
And as far as the Army's basic being a joke, I challenge that 15 year old to join up and go through Army basic and let us know how much of a joke it is afterward. While there is some intra-service rivalries, Marines and Army both respect each other, especially since we have been fighting side by side for each other's life in Iraq the past few years. They go to many of our schools and vice versa. The big difference in the basic trainings (or boot camp for the Marines) is that every Marine trains as a rifleman, and they all go through combat arms oriented training in Boot. The Army's Combat Arms Basics are fairly identical. Our combat support and combat service support basics WERE toned down, but they have strengthened them since the war began. I have been in Combat Arms my entire time, and I can say without a doubt you will find plenty of challenge here if you do the Combat Arms path.
One parting word: Make sure this is what you want. It's not the movies, it's not TV. The amount of time you will spend doing monotonous boring tasks will far outweight the time you spend doing "cool" exciting stuff. (Although there are many of those as well.) You will be cold wet and tired a lot. And oh yeah, there is that whole war thing. We have all lost good friends (I have personally lost 5 good friends including 2 Soldiers I led in my past Platoon over there.) It's hard and not fun. But it's my duty, and something I can say I sacrificed myself for. There aren't many jobs out there where you can say you know you may die willingly for when you go to work. If you do it, do it for the honor of it. Without a doubt, read the recent Sports Illustrated article about Pat Tillman (the issue with him on the cover.) If the military is right for you, it will inspire the hell out of you. (He was an incredible person, and a great role model and great Ranger.) If the military is not for you, it will most likely steer you away, and that's ok too.
Good luck, if you need further help or are interested in getting in a specific unit, let me know and I will help you out. Sorry my post was so long guys! Hope this helped.- Will