This is their enterprise-grade/high-performance Pro card. They sell a non-Pro one for $49.95, which is probably more on par with the quality you got.

I've had 2 off-brand eSATA ExpressCards I picked up for about what you paid, both of them needed drivers. What kind of card are you using that doesn't (and more specifically what chipset is it using)?

On the plus side, Sonnet's drivers work with my off-brand cards, which is a good thing because there's zero support for the off-brand ones, and Silicon Image (which makes the chips in most of these things) stopped providing timely driver updates a long time ago, so it's on the shoulders of third-parties, like Sonnet.

I am using a JMicron JMB360 chipset. The only time I actually needed a driver was for when I use it in Bootcamp. I actually got it for $17 on Amazon. In Snow Leopard it is just plug-and-play. The full product name is Syba SD-EXPC34-1S2 JMB Chipset 1x e-SATA Ports, 34mm, Up to 3.0Gb/s ExpressCard.

I actually noticed this weekend when I was setting up a new MacBook Pro 17" that the ExpressCard I have is recognized without any other drivers.

But in order to get my 4-bay eSATA enclosure to properly mount, I needed to install the Sonnet drivers. In my case with a card based on the SiliconImage 3132 chipset, it doesn't appear that Mac OS X's drivers natively support port-multiplier enclosures.