I have nowhere close to the number of interviews other superstars on this forum have, but enough to be cautiously optimistic.  From talking to other applicants and observing trends these past three months, this is what I've noted:
-Like junkemail86 said, big name letters seem to be very key to securing many interviews.  A strong personal LOR is still a definite, but if you can get it from a really prominent ophthalmologist (well published, editor of a journal, trained at big name program etc.) it will open the floodgates.  My interviewers have said I have good LORs but unfortunately one of my LORs is not very well known and the other was only known well in the southeast.  I think that the LOR will be vital in strong clinical programs and some hybrid ones.
-Step score is important but I think people overestimate how important the actual score is.  This is mainly used either as a screen or a way to determine ties for an interview.  I don't think having a 250 vs 260 matters as long as you clear the cut-off.  There may be a few programs that give extra weight to actual performance come rank list time, but none that I know of specifically. 
-Research is key, and in the future I think that having some sort of research or a case report is going to be required getting interviews outside your geographic region or even your home institution.  I have a first author clinical ophtho paper which interviewers brought up but nothing compared to the other applicants with more papers and presentations than they can count on their fingers (and toes for a few).  However this may open up more academic programs rather than strong clinical ones.  
-Where you're from matters.  This sucks, and I don't agree with it one bit (as I'm sure many other applicants) but this is the hard fact of life.  Many applicants have shared the same sentiment.  If you're from the Midwest, expect lots of interviews in the Mideast and parts of Southeast.  If you're from the Southeast, good luck breaking past the Mason-Dixon line or west of the Mississippi River (unless you went to Emory, Vandy, Duke, or UMiami).  Northeast and West Coast schools tend to do better because they have better-known medical schools.  Like junkemail86 said, where you go to medical school matters.  I'm from a little-known state school (despite what everyone else says here) and I'm feeling the pain.  What helped me get the few interviews outside of my region was my away rotation and that I had spent some time in the Northeast.
-Away rotation.  Controversial but if you come from a program with few/no big-wigs and a small department, you HAVE to do this.  Try to get it in June/July if possible because August will be cutting it too close for a LOR (you need to get your app in by early Sept).  At schools with top ophtho programs some applicants don't recommend this but if you're not one of those lucky individuals there's almost no risk doing an away rotation at a good program.  The reason so is that if you do very well and shine, you will get an interview you would've likely not have received otherwise.  In addition, you will get to know attendings and residents well, so if you brought your A-game and did well on your rotation and interview, they may fight on your behalf.  In retrospect I wish I had either done my away earlier or scheduled an additional away rotation.
-Grades.  Clinical grades probably won't matter that much getting an interview.  However, they may come up during an interview so don't blow off your third year to solely pursue ophthalmology.
I may be changing my tune post-match day but these are my two cents on the interview trail so far.