The pair is convenient, front and back lights. The are very bright and I at least feel like the cars on the streets of NYC can see them. I like that they are rechargeable because I use them very regularly and I don't have to buy batteries (inconvenient and the extra cost of this pair probably evens out over time with cheaper options). The different flashing patterns are potentially useful. The silicon housing is easy to wrap around the handle bars or the seat post and it's quick to take them off if I'm going to lock my bike up outside.
Why only four stars: The black cover over the front of the red light fell off after a few weeks (white light cover is still on). I could super glue it back on, I just haven't. The light still works fine, even in rain. Also, you don't get any USB cable, so you'll need to potentially rig a charging option (no problem for me).
Note: These things do run out of juice, so make sure it's charged enough before you head out. My red light was dead when I went out to ride tonight, went anyway, but just keep that in mind.
I would recommend these to a friend, I'm very happy with them.