I've been taking over 3grams of choline for over a month now and I can tell you that I would not be without it. It's my second favorite supplement next to wheatgrass (or supergreens).
As for safety. One serving size IS 15 grams of lecithin which contains 3250 grams of choline. Says it on the nutrition facts! 
But you've got to get it in the granule form, not in the capsules. Capsules are way too small.