I'm using h4 bi led. CSP based.
Guys who said they don't feel much difference using LEDs, there are important design variations that could be hampering output. Also, as one brother pointed out, if while installing the led bulb, the orientation of the bulb isn't what it's supposed to be, you won't get light where it needs to be.
As for dippers, LEDs flash pretty fast, and damn bright. So for people going at donkey speed in the F1 lane, two dips are enough to communicate you mean business. (Try not to abuse the added power)
LEDs will NOT be a saviour if your lenses are dirty on the inside, or yellowed, or scratched, or headlights misaligned.
Rest, try use a bulb design that matches as close as possible with stock halogen bulb design.
Lastly, nothing matches HIDs in HID enclosures, or factory LEDs. Nothing.