I previously had a Cat Eye HL EL-500 which was far brighter, but also way more bulky. Unfortunately it broke, and they no longer make it, so I bought the cheaper sibling. However, it does make me wonder how durable Cat Eye lights are. They feel very well made, but my old one broke after being dropped from about handlebar height, once. My new one (a cheaper one), has fallen once, while biking (didn't fully attach it) and it still functions perfectly, so I hope they've fixed the breaking issue, or that I just got a bad one last time.
As for practicallity, its perfect size in that it dissapears in a pocket (and obviously in a backpack). Its plenty bright to be seen, and has a flashing mode and always on, so you can easily draw attention to yourself. I love the way the on-off switch works in that unlike my tail light, you don't need to cycle through the different modes to turn it on and off.