The only additional threats I can see would be threats against your PC directly, rather than your traffic.
Am I wrong?
It's much, much harder (but not impossible) to do this on a hard-wired connection - there's a useful discussion as to why here: http://news.ycombinator.com/item?id=1828201
That's why I said that the only additional risks I can see of an public Wifi is local attacks directly against your machine such as someone port scanning your laptop to look for vulnerable service or open fileshares, etc.
Think about it, say you want to grab somebody's credentials for a popular website. Do you a) hack into their ISP or b) follow them to a coffeeshop and open up Firesheep. What's the easiest angle you are going to take? Local network sniffing isn't the trivial example of sniffing, it's the most vulnerable and probably most exploited target. (Just ask Google.)
At my home and office you have to contend with WPA2-Enterprise (it's easy to set up at home, so I did). You'd need to get hard-wired access to my home, and pull some ARP trickery to sniff my last-mile infrastructure. We have 802.1x on the Ethernet ports at the office, so no dice there.
You're right, to a point. And the effective response is to make sure you're always protected as well as you can, instead of going into a "shields up!" situation only when your perceived risk is higher.
So, the number of people who could conceivably be eavesdropping goes from a few (unscrupulous IT workers and law enforcement) to very many (everyone who can figure out a WiFi packet sniffer).
When someone brings out the "ARP poisoning" add-on for Firefox maybe it will fuel debate on other types of attack :)