any good quality worm castings will improve the overall quality of your soil or soilless mix. I would for sure not grow without it ever. THe benefits you recieve are too numerous to go without. Not to mention the amazing compost tea you can make from it with a little molasses. Organic growing is the best and only way, I would like to try organic hydro one day just to try it out.
When I mix up my soil, i use 5 parts peet moss, with 1 part worm castings. Got this mixture out of Weed World mag. I have used this mixture for the last 2 grows, currently on my third, and things have been good so far, I have had no problems what at all with nutrient burn or anything like that.. So far so good!