I understand that I can use 110V lights on 220V with a stepdown transformer. However in my understanding the stepdown transformer dosent change the 60 cycle to the 50 cycles we use in the U.S. Would this difference in cycles provide any kind of a problem with the 110V lights?
Stepdown transformers are bulky and inefficient for lighting; you're best off just buying 220v globes if they're available for the units you own/use. Otherwise an elegent solution I've used is to wire up pigtails to use two 120v units in series. This solution is almost weightless, almost free and further solves the local connector adaptation. I'll make up the US household part before I travel and go to a local hardware store any buy the plug in connector when I arrive. Several minutes later I'm on the air. As long as you are using any even number of units your fine, otherwise use a dummy 120v load for the odd units.
I use transformers to power my 110 lights in my 220 house in Germany. I haven't experienced any noticable affect to the lamps themselves, but I agree with the other post that they are bulky and heavy (like a car battery).
If you are talking about fluorescent lighting, they flicker at whatever hertz you are using, so a 50Hz socket will cause the lamp to flicker at 50HZ, which looks awful on U.S. cameras shooting at 60fps. You can mask this in-camera by setting the shutter to 1/00th sec. but this eats about a stop of light.
If you are using halogen lights, its probably much easier just to buy 220 version bulbs and simple plug adapters.