Thanks, that is all very helpful information. I will definitely check out the physicsgre forums.
As far as "long shots, reasonable, and safeties," what sort of ranking ranges would you consider? Long shots being anything in the top 25?
Also, I am planning on applying to University of Rochester. I believe they're ranked 44 or somewhere around there, but they are ranked 6 in AMO. Since I apply to the graduate program in physics and not specifically in AMO, does anyone have any insight whether they would be as hard to get into as a 6th ranked school, or a 44th ranked school. This type of scenario applies to more than just U of R, but it makes a good example.
It still depends on how you do on the PGRE. Nearly everyone admits that the PGRE is not a good indicator of graduate school success, but they still need it for admissions to help normalize GPAs obtained from different schools. I've talked to several admissions professors about this and I get the feeling they look for a certain cutoff score, and after that they care much more about research experience, letters, and grades. This way they will not accept people who did nothing except study for the PGRE, and still accept someone who did decently but not great, but has good research experience and promising letters. In other words, the PGRE probably will not be a deciding factor in their decision about you. If a committee was deciding between someone in the 70th percentile and someone in the 80th, they would probably make the decision based on something else and not just pick the person with the better score. In fact, my grad school cohort had scores ranging from the 30's all the way up to near perfect.
Here is another point you may not have considered yet. You're research experience does sound a little weak, especially since you won't be very far along in your senior project. You could potentially benefit greatly by taking a gap year, and you could finish your project and get a paper and study more for the PGRE before applying. That's not to say you shouldn't try this time around, but it's something to keep in mind.
As for a school like Rochester, it is certainly easier to get into compared to a school ranked 6th overall that is also strong in AMO. But it's also probably harder to get into compared to a similarly ranked school that isn't in the top rankings for some sub-field. This is a good thing for you, since really the most important thing for your success is who you're advisor will be, not the name of your school. But even though you apply to the graduate program, they do consider what you say your intended sub-field will be. More people applying to Rochester probably say they want to do AMO compared to astrophysics, so it's probably harder to get into for someone with a stated interest in AMO compared to astrophysics.