Turns out that this is actually fairly bright, even if it's at the low end of the Cateye lineup. It's brighter than my ViewPoint Lazer that advertises having a 1W Luxeon. This has a tiny little LED in a reflector, without any fancy Cateye lenses. Like most current lights, it has a fairly bright hot spot with a wide circle of brightness.
There's a plain flash mode and a steady mode. You have to hold down the power button to shut it off, if you just press it, it'll switch between blink and steady.
It has a fairly long battery life and takes four AA batteries, the only problem being that it gets fairly dim over time as the battery runs out.
Like all good light makers, Cateye wants you to be able to mount the light almost everywhere. The way they did this was a nut that you turn that pulls the strap on the mount. Which means that if you are never going to mount it anywhere else, you can cut the excess part of the strap off, or you have this thing sticking out. And it takes a lot of turning to get it mounted. I guess there are some situations where it might be better to mount, but otherwise it's kind of obnoxious.
I kind of wish Cateye would make all of their lights with a mount like the HL-EL450 that lets you mount it on the stem.
Right now, the HL-EL320 is in foglight position on my fork. I use a Minoura Besso to create an extra lower mounting point.