Pros: Quick release.
Bike mount.
Clip for jerseys and backpacks.
Different blinking modes.
Weather seals look to be pretty good although I haven't had to test it yet.
Light and compact.

Cons: I don't really see one yet

Other Thoughts: For the price, I couldn't believe they included both a clip and a quick release seat post mount. It's a pretty nice feature if someone bikes and runs.

Bottomline: For the price, this is about as good a bicycle warning light as it gets. Buy one! I probably will buy another just to have an extra.

Pros: Very simple construction, yet feels very solid to hold.
I bought 8 of these for me and my brothers and none of them have broken yet..
So yeah!
^^
+They come in retail packaging! (not the best packaging, but shhh!)

Cons: Takes AAA batts.. grrr.
I hate AAA.

Other Thoughts: I just wish there were cheap AA variants.
(hint hint DX) :P
These is a multitude of modes, although I only use the SOLID light one.
Comes with a clip to attach to nearly anything flat, but also comes with a bike handlebar attachment!

Bottomline: Nothing wrong with these lights, for their price you really go wrong, right?

Pros: The LEDs are nice and bright with good battery life. I like having the option to choose a flashing, partially flashing, or solid light. Fit well on my Specialized Rock Hopper bike. Light can double as a reflector.

Cons: It would be nice if it held AA batteries for extra long runtimes but I like how this is very light weight since it's mounted on my saddle bag.

Other Thoughts: Infrequent nighttime bikers may want to look at getting some of the low self discharge (LSD) NI-MH cells for this as standard rechargables will lose >30% of their charge each month.

Bottomline: Buy it if you need it! Much cheaper than anything I've found locally and I don't have to worry too much about it falling off or getting stolen.

Pros: Small, lightweight, sleek styling (doesn't look as much like a toy as some) slightly more red and less orange than pictured, runs a long time on 2 x AAA batteries, brighter than I thought it would be, rubber gasket and power button for good water resistance. Easy to remove from mounting clip.

Cons: Fricton tabs instead of spring battery contacts, greatly reduced brightness after ~ 40 hours (flashing mode) running on NiMH (but kept running much longer), minimal light output to sides (but I didn't want a large, thick light), uses AAA instead of AA cells so runtime is shorter (but smaller and lighter weight due to it). I wish it had a separate battery hatch with a rubber gasket instead of popping lens off to swap batteries, but it would have to be much larger to do that and I wanted it small.

Other Thoughts: I assumed it had low-bin LEDs so I swapped one out for an 8K MCD red I had lying around. I was wrong, the original LEDs are
brighter AND wider angle than 8K! It's a cheap design with flashing controller in epoxy on a thin strip board but that makes it lightweight, and low cost is good! There is chrome panel behind red lens to hold batteries and reflect more light and it all fits together well enough. I only wish it had one LED pointing to each side also. I had doubts it would be bright enough as other rear lights had more LEDs but it is plenty bright for my use and should run longer and be less ugly/obtrusive due to sleek smaller size. At such a low price I don't even have to worry about it being stolen. I wish it ONLY had two run modes, always on and flashing so I didn't have to press power button several times to turn it off but this is minor.

Bottomline: When I bought it, DealExtreme had fewer rear lights on their 'site but they added several recently that are very similar except more LEDs. I think it's enough light but might choose sku 5749 next time to use AA instead of AAA cells. The picture makes it look thicker than others but it is just smaller width and height with about same thickness. I am happy with it for the price and use it regularly. To get it delivered for this price is amazing.