I'm used to retrofitting LED's into existing tanks and have been doing it for nearly 5 years now so it becomes commonplace to me and I rarely get excited anymore.
Yesterday, I pulled a 4x54w T5 off of a 6' long 150 and replaced it with 3) D120's. there was quite a difference in light to say the least.
When the client and his wife saw it, they were literally stunned and both had one of those, Wow! reactions. I hadn't seen a reaction on middle aged people like that for a long time. It's nice to hear how people react to positive changes in their tank.
Just sayin.