An instrument rating definately helped me. I will admit my experience differs from some others that had similar prior time going in and "to each his own" definately applies. I had about 250 hrs. with a private/multi/instrument. The big difference it made in primary was in the instrument phases. I definately had a leg up, but I caveat that (building on with Uncle said) that a large chunk of what I had learned before had to be dumped and relearned the way the Navy wanted it. You don't want to be that guy with prior time that's simply unteachable. What helps is the experience on the radio, basic attitude instrument flying, and just general common sense in the cockpit as it applies to instruments.
The proof positive of this theory was evident in my primary selection. One of my best friends and formation partner in primary, who was (and still is) as good if not better of a pilot than I was, was in the running with me. He had no prior experience, and we both put tailhook as our first choice. When selection day came, he mentioned that he had around a 51 NSS (right at the tailhook cutoff) and he was sweating it a little bit. I was shocked, because after flying formation with him, and based on his reputation, I thought he had done better than me! It turned out my NSS was over 15 pts. higher, and you could trace it back to basic and radio instrument phases. We both ended up getting our first choices, but I was definately in a much more comfortable position going in.
Aside from all of that, my advice to you is get your eyes checked by a Navy flight surgeon. I had 20/25 vision and still needed PRK due to the amount of astigmatism in my eyes. No sense doing anything else until you've got that locked down. Then at the very least get some instrument instruction time in the airplane. It can't hurt as long as you don't develop stubborn habbits.
