To start:
I have found this to be the best LED light for my needs. I have had some vision issues, and I need something to provide contrast during those dark gigs.

Two warnings, though;
Be careful about a long gig; remember to turn it off on breaks and such. It lasts around 3-3.5 hours, then it just goes dark. That's so it can remain at full power, rather than fading gradually through the gig. This is documented, however, so I did not downgrade the rating for that.

My reason for the 4-star is as follows:
It likes to fall off the stand. This has happened twice now. The springs that hold the light to the stand are sorely lacking. Keep in mind, this light is made of metal (aluminum) which is great, but makes it heavy.
I like my stand tilted back... not that much, just a bit. If I go even a little too much, this top-heavy light just lets go! Needless to say, this is a bit of a distraction during a gig!
I have had to rig up a device that keeps it from doing this, (Forget magnets, it's aluminum) which is inconvenient when compared to just snapping on the light.

I wonder if I got one with weak springs? Has anyone else had this happen?

This unit is very bright and does evenly cover two-page music from top to bottom and edge to edge. It seems impossibly bright for a battery-powered unit. I love that it is not the "ultra-blue" color that irritates my eyes, but is closer to "soft-white" which is far nicer. The battery has easily powered the unit through 90 minute concerts at full brightness, and I keep it plugged in and on my Manhasset stand at home; it the field it fits beautifully on my Peak travel stand. My only minor complaint is how high it extends above the stand when mounted; seeing the conductor means my music is lower and farther from my view of the conductor. This visual disconnect increases as the desk is more strongly tilted. I understand that the height is needed to allow a standard band/orchestra folder to fit under it, and the distance the LEDs are above the plane of the desk is needed for that nice even illumination. But this is the compromise you have. A very special bonus for the conductor and the audience is that the very bright light does NOT shine under/through the housing toward either of those people; this is far superior to the "goose neck" types.

This is by far the best light I've tried. Just played a trio concert where I needed three pages up at a time and it worked quite well - not quite covering all three pages, but making it possible to play at least. Expensive, so I hope it lasts, but the brightness (and dimmer switch) are far better than anything else I've tried. Sturdy, light weight, recharge lasts a long time. Lifesaver for old eyes!

My wife, a bassoon player, loves this light. Concert stages and orchestra pits often have low light and the usual lights for music stands aren't always enough for her. This one is very bright and easily covers the width of a standard Manhassett music stand. It can be dimmed as needed. If you're always wanting more light, this one works well and it's worth the cost.

Best music stand light for dim lighting conditions. I've tried other less expensive lights with a bar of LEDs and clip-on gooseneck, but had problems seeing the bottom of the music. This lamp lights up two full pages evenly, and did the trick during a holiday concert where the ambient lighting was atrocious. I lent my other gooseneck lamp to a fellow musician, but she still had trouble seeing the music.

I keep the lamp plugged in so it is ready for gigs. The longest I've used it off the charge is 1.5 hours, so can't really speak to the advertised battery life. But for the time I used it, I had it on full brightness and never lost effectiveness. There is a very long charging cord you can use for power if necessary, I would suggest bringing a backup light if you need it for longer than 3 hours in case there is no electrical outlet available. Also, the light is designed to clip on to a solid music stand, but works fine with my plastic folding stand which has a solid table. I was able to fit it right in the stand bag. I wouldn't recommend using the lamp with one of those flimsy metal folding stands, since it will not carry the weight of the lamp.