I tend to pack pretty light, plus I have very strong ankles so I only wear trail runners, unless it's winter in the high country, even when I was a pro mountain guide. The old Army addage of 1 pound on the feet equals 3 pounds on the back is true and I find with lightweight footwear (and a lighter pack) I have much more energy at the end of the day and I can cover more miles. I also tend to be pretty hot, so typically I avoid Gore-tex and other waterproof models as they just don't breathe well enough for me. eVent is finally starting to be used in more and more shoes, so that may be just the ticket if you do need a waterproof shoe.
My favorite trail runners are from Montrail and I have owned 6 or 7 pairs, with my Hardrocks being my current favorite, but the Hurricane Ridges are great too. I wore 2 pairs of a discontinued model on a 900 mile trek in Japan and they were great! I believe that the first person to complete the Coast to Coast trail also wore a pair of Montrail trail runners.
As mentioned above Merrels are good and I liked by Stretch Chameleons. I also have one pair of Solamon's that I really like (XA Pro Comp, I think).
Go to your local outdoor shops and running stores and see what they have and start doing some research on the internet. Ultimately you need to find a pair that fit your feet and any foot issues you may have. The running stores can tell you what type of shoe you need based on how you pronate and also your weight.
Regardless, do yourself a favor and get a good pair of insoles from SuperFeet, Montrail or Soles.