I recorded a two nearly identical videos using my 3G S and my jailbroken 3G. I did this to provide a sample of video quality across the two devices.
Here is the cycorder video (link to my me.com gallery)
Here is the 3G S video (link to my me.com gallery)
Some immediate differences are video size. The 3G Cycorder videos are 384 x 288 pixels while the 3G S videos are 640 x 480. The file sizes are roughly identical, with only a 2MB difference between the two. The bit rate is slightly higher on the 3G S video as well.
Overall the quality on both videos is pretty good. I wasn’t really wowed by ether one but cycorder has improved quite a bit and holds its own for those not wanting to buy the 3G S.