I purchased my dl1608 early this year after borrowing one to do a show. My old mixer was an Allen & Heath Mixwiz3, used with a rack of analog eq's, comp's and effects. I've done many shows now using the Mackie, and many at the same clubs and same band as before. At every show, the sound not only is as good but has improved. I feel I'm getting better, clearer definition between the instruments, and the ability to walk the room and mix makes for a better sound throughout.
As far as output, I see no difference at all. Every channel has a HPF, and I use it as needed except on the kick and bass guitar. The gates work very effectively if you have a ringing drum kit. I use the comp's on vocals very lightly. The eq's are different than what I'm used to, and I find that I use them in an extreme fashion, with steeper filter curves and I use them to add considerably when needed. These eq's are digital and free from noise in my opinion.
I'm using my board with a JBL PRX portable system. I've used the on-board effects a few times and find them adequate, but for high-end effects I recommend a separate box.