I should say that I am not a big fan of bridemaids dresses. In fact, I didn't have bridesmaids at my wedding because I wanted all of my friends to relax and have a good time. That being said, I was a bridesmaid in a wedding, and she used David's Bridal separates for her bridesmaids.
I do like the convenience factor of using David's Bridal - I was in a different state at the time, and just had to go to my local store to take care of things. The price was also reasonable, but I have to say that the dress left some things to be desired!
The color was a weird shade of purple, but it did match the other dresses. It worked well for the other ladies with lighter skin tones, but was just not a good color for me. The style also did not suit me well, since I am fairly tall. Again, it worked well for the rest of the bridesmaids - 3 people out of 4 isn't bad! That being said, these sorts of thing are more a matter of personal opinion.
The worst part for me was the material and the construction quality. I got a horrible rash while having it fitted (the dress was only on for about 10 minutes). I had it dry-cleaned prior to the wedding, and thankfully I didn't have any issues. Still, you should be able to try on a dress without having that bad of a reaction (I don't have extremely sensitive skin).
Also, the zipper broke on my skirt the day of the wedding - it wasn't a size issue, it was just poorly made.
All in all, I am not sure if I would recommend David's Bridal or not. None of the other bridesmaids had any issues that I know of - I think I might have been an isolated incident.