There are many parts to select that affect whether it runs well - more than 6 per cylinder (idle jet, idle jet holder, main jet, emulsion tube, air bleed, choke, accelerator jet are the main ones) and 3 units to synchronise. So there’s a lot to set up. You either have to really like playing at it or go to a rolling road and pay for the pleasure.
Once they’re setup it’s ok to stay on top of and they look better and make better noises than SUs. They even make more power ultimately, with the right engine and other bits.