I've heard of SEVERAL people having success using LEDs with planted aquariums. I say if you can afford it and don't mind giving it a try, go for it. Just don't add any fish unless you know for sure your plants are thriving well under the LEDs.
Let me add a few cents to this...
LED lighting creates several concerns when it comes to plants:
- Color temperature - Always check the output color temperature rating (K value) of the bulbs. Several color bulbs may be required to fulfil the entire spectrum needs of your plants.
- Actual wattage of light output as opposed to wattage of electricity used. This may sound confusing, but be aware that the wattage on an LED bulb is (IMO/E) not directly converted to traditional wattage as from an incandescent bulb or a fluorescent tube. Make sure you provide ample light output for your plants. I go by wattage of electricity being used because of the various qualities of LED light that may skew the perceived wattage of output. e.g. We all know those "super bright" single bulb led flashlights only seem very bright because of the color of the light. Actual light output value in terms of what the plant would receive from the bulb is most likely lower than what you may perceive it to be.
However, I had a coworker once who grew plants under his desk at work. He built his own LED array for the vines to grow on, but one thing he did was to vary the color of the led lights in a rainbow-like progression from red to orange, yellow, blue, green, purple, etc. I think this color changing effect he created accounted for his success in providing adequate lighting conditions for his plants.
There are several led hood setups designed for aquariums, but whether they were designed with plants in mind is a different question. Make sure to check outputs and color temps, and if you do spring to buy one, I'd suggest testing it on another tank before relying on it to keep your NPT healthy.
You may need to fact-check some of this wattage information with some sort of scientist (aka Google) to make sure that I'm right, but this is the general understanding I've come to have over time.