Pros: It is impossible to see that there is a camera inside the pen if you don't know it from before.
The pen works great and the battery is pretty good. (about 2hours)
The quality is very good. I have had mine for about 6 months and it still do work.

Cons: The camera films in a pretty low resolution, but what can you expect from a such small thing? Actually, it ain't that bad because of the size.
The sound quality is not that good when it get noisy.

Other Thoughts: If you think the camera seems interesting, buy it!
But i stopped using it after 3 weeks because of i got bored of it.

Bottomline: It is very fun to play with, but in many countries it is illegal to film people with their permission.

Pros: the price of it is good for a camera
the quality is good only if it is controlled with a good speed
the pen actually works as a real pen
the ink is good and does not smudge
the pen records accurately

Cons: the pen seems to be a little too big
the sound quality on it seems to be really poor
if the ink runs out there will be a big uh oh
the built quality could be better but i guess it is like that because of the price

Bottomline: Buy it because you will not regret the item and because you can use it for whatever you want without being caught like recording test :p

Pros: Works reasonably well, as a camera, a pen, and as a usb drive. Data rates when transferring files onto/off the drive are quite fast. Video capture was clear and in focus. When i first got the device and charged it up, i was lucky to get a 30 minute recording out of it. After a few charge/discharge cycles the recording time seems to have increased with my last test coming in at over 90 minutes for a single recording. For those interested this was literally just over a 1gb file (1090Mb).

Cons: Aside from the audio issues outlined in previous reviews, the biggest downside was the jerkiness if a sudden movement occurred in the field of view. As long as the movement was smooth and the only motion was that of individual objects, the camera was able to keep up with the movement.
When i initially got the device i managed to get it to crash once or twice when unplugging it from the computer after shutting the device down within windows. I later found that you also need to hit the power button to turn the device off before unplugging it, otherwise you run the risk of crashing the o/s on the pen and needing to reset/reinitialise the pen.

Other Thoughts: Good video quality, though i should have gotten the higher resolution gizmo. Still fun to play with and handy if you are ever in a dodgy situation.

Bottomline: Aside from a few very small bugs (which you learn to work around very quickly), it is worth the money if you need or want such a device.

Pros: The video is better than you would expect.
Nobody pays attention to a teacher with a pen / laser pointer in his pocket.

Cons: The audio is worse than you can imagine. There are loud poofs whenever it bangs against my shirt, which makes the audio useless. I would carry a digital voice recorder if I needed audio.
This cheap piece of junk will break very quickly. Don't try to clip in on a pair of jeans, as the clip will break off. Don't try to write with it or the ink holding part will break. (At least it does not leak.) Don't use it any more than is absolutely neccessary.

Other Thoughts: The blue LED is lit when recording, but it is not visible given the way the pen sits in a shirt pocket. If all else fails, say your flashlight pen is broken, or use a bit of electrical tape.
The LED that makes this pen much easier to use than DX's other spy gadgets. Just hold the button on top until it powers up (the yellow led lights up.) Wait 60 seconds, and press the button again to start recording (the blue LED lights up.) Press the button again to go onto standby mode.

Bottomline: This is the best way to get started on DX's spy cameras.
I do wish DX would build a laser pointer into one of these, and make it much more rugged.