I've been told speeds will slow down the longer the cord...not sure how significant the attenuation is on USB.
A proper USB 2.0 cable can only be 5m long, maximum. Assuming it's correctly made, all modes will work properly at their intended maximum speeds. It's certainly true that really shoddy cables, or those made beyond spec length, might cause a negotiation to a slower speed... or simply fail.
Someone already beat me to recommending monoprice.com... I just ordered four Droid cables today.
This is the "micro-B" cable, and usually you want "standard-A" at the other end. Watch out... there are lots of devices out that claim to use a "micro-USB" connector, but most of these use the "micro-AB" connector, which can act either as target or host for a USB device. So my in-car Nav unit can read music and video from a USB stick, my camcorder can backup video from flash to a USB storage device, my pocket camera can speak to a printer, etc. Also, a micro-B is about the same width as a mini-B, just thinner... don't confuse them.
The micro-B connector was supposedly designed to last longer... they claim 10,000 plug/unplug cycles... though I would still treat it gently. The mini-USB connector is only rated for 500 plug/unplug cycles. You don't care about cable end so much, but it would suck if your shiny new DROID couldn't be charged reliably after a few months. Well, there's always an external battery charger option...
Curiously, there's only one "mini" connector... they're all "on-the-go" type. And there's no standard "on-the-go" connector... the specs were created after the standard versions had been speced.
