I use USB ethernet on rev A and at max I get 8Mbyte/s.
Don't know how surfing the internet can be slower than MB, it's not much power hungry operation.
My wireless MBA performs no differently than my wired PC through the cable modem (both run around 9800 kb/s download and 950 upload). I notice no differences running web sites between my MBA and my Macbook Pro or iMac.