McDonald's is a great first job. I've been there a little over a year (I'm 17), and I wouldn't dream of quitting anytime soon. It was my first real job, and I love it. The people are great; you will make some really good friendships with people you wouldn't meet in any other environment. If you have friends there, the experience will be that much better. If you want a fast paced environment, it is a good place to work. The pace may often seem too fast. It can get very stressful. One of my co-workers read somewhere that if you can handle the stress of working at McDonald's for a year, you can handle the stress of any job out there. It's a good place to work for kids because the schedualling is so flexable. I'm involved in lots of extracurricular activities and I have no problem getting time off for them. Another great thing about it is that employers really like to hire people who have worked at McDonald's. The system is very structured and standing around is usually not tolerated. This is something that will give you an edge when seeking employment in the future.
There are of course drawbacks. If you have a hard time with stress, it's not a great job. I personally thrive on it. Also, if you're a slacker, you won't do well. But you seem pretty organized, actively seeking summer employment and having a list and all, so I don't think that you'll have too much of a problem if McDonald's is the place where you choose to work.
I personally believe that everybody should have the experience of working in food service. It really opens your eyes. You gain good people skills, too. You are probably going to see a lot of negative postings in response to your letter. Take them with a huge grain of salt. Don't take my word or anybody else's word too seriously. I recommend that you try it for yourself and see how you like it. You don't have to stay there forever, it isn't the military. Good luck to you in your job search. And do keep us posted.