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That's slower than a lot of USB drives...so it'd probably be frustrating, if it was even workable at all.
 
I'm not expert on Expresscard/34, but this was just about the first thing that came up while googling:

http://www.transcendusa.com/products/moddetail.asp?modno=162

Has about the same speed as the better USB 2.0 drives. I'm sure you can probably find something a bit faster, but as far as I know expresscard drives don't compare to internal drives in terms of speed, at all. A lot of them are restricted to USB 2.0 speed because that's how they're configured.

But, again, I don't know what the minimum requirements for a boot drive are. USB 2.0 speeds are certainly usable, but I'm sure they'll be a PITA.
 
Expresscard SSD's come in two flavors, differentiated by the bus they connect on.

The one linked in the OP probably connects via the USB bus, hence its slow speed.

SSDs such as this connect on the PCI-E bus (2.5 Gbit/s max) and will be much faster, but I don't know how easy it would for you to boot from it, if at all.
 
Expresscard SSD's come in two flavors, differentiated by the bus they connect on.

The one linked in the OP probably connects via the USB bus, hence its slow speed.

SSDs such as this connect on the PCI-E bus (2.5 Gbit/s max) and will be much faster, but I don't know how easy it would for you to boot from it, if at all.

One of the reviews is a mac user booting from it:
Amazing for Macbook Pro 4,1
Reviewed By: on 3/13/2010
Tech Level: high - Ownership: 1 day to 1 week
Pros: This thing is FAST safari launches before the dock icon can even bounce once, itunes loads twice as fast, same for mail and ical. Installing this card could not be easier just slide it in. I use this as the boot drive running Snow Leopard 10.6.2 and use a Seagate momentus 7200.4 for itunes library and virtual machine. But using the solidgo as a boot and application drive makes a world of difference.
 
Expresscard SSD's come in two flavors, differentiated by the bus they connect on.

The one linked in the OP probably connects via the USB bus, hence its slow speed.

SSDs such as this connect on the PCI-E bus (2.5 Gbit/s max) and will be much faster, but I don't know how easy it would for you to boot from it, if at all.

In my case, it's easy~ What I need to do is just move the VM file to the express card SSD :)
 
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