IMHO and experience, yes. But make sure you use them in the ways that will get you the best results. At the expense of repeating what others have said, LED's are much better for vegging than flowering, mostly because of light penetration. However, they do make LED lights that are specifically meant for flowering, meaning they have more lights of the red spectrum which flowering plants love.
If you're new to LED's and want to start at the top, check out cree led lights, or manufacturers that use primarily cree LED's. The reason for this is that many LED's have gotten a bad rap from knockoff's and low quality manufacturers in China. I currently use a Blackstar 180w LED for my veg tent, and I'm so happy with it I plan on getting two more to break up my veg tent to one mother/clone tent, and another tent dedicated to growing larger veg plants before I put them in my flower tent. So in the end, I'll have one 180w over the two mothers I have, and cfl's over my clones and two 180w over the vegging plants (in two 2'x4' tents). Its important to remember that the big benefit of LED's is the low power usage and low heat, which means that you can get the plants within inches without any adverse effects! But the big benefit also means that the closeness will keep your other plants not in direct light from reaping the great benefits so your footprint will be smaller with LED's vs. HID.
Also, make sure you look for the 3w diodes. Someone referenced 1w or more, but IMO 3w's are the standard you should be shooting for. And again, I'm repeating someone else's thoughts but make sure they have multiple spectrums since each diode puts out one specific wavelength only and your plants use a variety of the visible (and nonvisible) light.
So to sum, yes! An emphatic yes! But do your homework, stay away from brands you can't find reviews for, and use the lights for their best purpose! Have fun, I know the heat and electricity savings I'm getting have changed my whole setup and understanding!