I can't really say that I have "trouble" but I would say that I haven't had glowing success either.
About a year ago I switched to a Kessil A350 and things looked pretty good overall. A few SPS frags started to lose color though while others looked great. I dropped the intensity and colors improved overall but I still had a few frags that were pale.
I switched to an AI Sol Blue a couple of months ago or so and things are pretty much the same. My tank is 20" deep and the Sol is about 8-9" over the water. My intensity is W:55%, B:60%, RB:70%.
I'd say that a lot of pieces look real good, some pieces look fairly good and a few pieces look horribly pale. The 3 pieces that just don't seem to like LEDs are:
-GARF purple bonsai
-Palmers Blue Milli
-unknown that I believe is acropora nana?
-Turquoise Stag
All 4 of the above came from a local reefer or board member and were under MH.
However, the following SPS have what I'd consider great color under my LEDs:
-Aqua SD Rainbow Milli
-Cali Tort
-Oregon Tort
-Forest Fire Digi
-Green Milli
-Pink Lemonade
On Monday my Lumatek ballast comes in and I'm going to be trying a 250W 14K DE in a Hamilton Cayman Sun pennant. I will definitely update this thread if I see significant changes in my SPS corals.
I don't think all the results are necessarily in on LEDs over SPS but I do believe that there are just certain SPS species that do not like LEDs for whatever reason. It doesn't mean that you can't have a really beautiful SPS tank under LEDs but I think you definitely lose some flexibility. Nobody wants to pay to have a high dollar LE frag overnighted to your door only to watch it lose all of it's color.
In my limited experience with LEDs I personally would say that they're fine for mixed reef or even for SPS dominant if you're not super serious or anal. However, if you're "hard core" about maximum color and rare corals or just a perfectionist then I'd say you may want to wait until the technology develops more. That's just my 2 cents after a year's experience with 2 types of LED fixtures.
Here's my build thread for anyone who wants to follow my switch from Sol Nano to 250W MH:
http://www.reefcentral.com/forums/showthread.php?t=2309786
Not to highjack of course. But it may be interesting for people who are curious about this topic to see how things go.