I have used, dissected and re-built the 10w straight up cold white version and have seen many people using them after googling the subject. Two 10w units lit up my 24" tank. Medium light I guesstimate.
They are a good idea if you can get them cheap and dont feel up to the task to building a led from the same led chips/drivers found dirt cheap. They come with water resistant
(claimed waterproofish but quality varies) casing if you plan on mounting them inside a hood. The glass is very thick and will eat up a lot of the light. Removed and the housing becomes a bit pointless imho, thus my diy comment below.
They added lots of led shimmer and grew my plants, removed them because I started to get algea problems (low tech non-co2 tank)
If you´re handy I would recommend buying the items needed from ebay and build one that suits youre needs. Much cheaper, and you can customize with active cooling different lenses/reflectors.
Edit: Found some old comparison pics of mine, dymax vs 10w flood led:
Some different test builds I made cpu heatsink with original reflector vs random heatsink found in electronics shop with 2x10w:
In the end this 36w par38 bulb was the best buy. Cheaper than flood, better focus, less shimmer, more light, easier to mount, better looking and so on...