My bridesmaids tried on both the ones from Nordstrom - they were pretty 'Eh' in person. Even though Davids Bridal blows a big one, they're dresses are relatively inexpensive and they have lots of colors/styles to choose from. Neither of my bridesmaids even needed any alterations!
Both Jcrew and Ann Taylors lines are pretty too, but they have limited color selection sometimes.
The most re-wearable BM dress I've worn was by Vera Wang. I honestly loved that dress. If I remember correctly, it wasn't that bad, price-wise -- around $250. The J. Crew ones look really pretty too, and definitely re-wearable.