I found that the two-port version (EC2S950) was the same price, so I chose to go that route. It arrived the other day, and I can report the same results as the other folks: downloads are quicker and more reliable. The only drawbacks I see are mechanical. It seems like the connector between the breakout harness and the card is pretty fragile, and pre-disposed to breakage in the near future.
I wish there was some easy way to strain relieve it, but short of mounting the laptop on a plywood panel I don't see any obvious solution. I'll be packing the old USB->RS232 adapter just in case.