When you say up to 10 devices, are you referring to 10 computers?
Could be up to a total of 10 computers, iPods, iPads, iPhones or any other device that uses wireless to connect.
Does Radio mode use DHCP?
It could, but you would run into a Double NAT situation on the network. Normally, you would configure the AirPort Express in "Bridge Mode" since the main router that it would connect to would already be setup to handle DHCP services.
can you fix mac addresses?
You mean "static addresses" here? Not if the Express is in Bridge Mode. Yes, if it is handling DHCP.
Does it have to be configured (like when adding a router at home onto a DSL modem - ie, gateway, subnet, etc.) or is it simply a plug and play on the ethernet system?
It will take a few minutes for you to assign a name to the device, establish a name for the wireless network and setup a password for the wireless. It might work "as is" out of the box, but there would be no security on the wireless so anyone in the area could log on.
Can I plug it into my ethernet at home and set it up and then plug it in there in Europe and it will work?
Yes, if you have a spare port on your main router to plug into. Once you have the device configured, it will retain its settings.
What is the dual band mode for on the Airport Extreme?
This allows faster wireless devices to connect to the new high speed 5 GHz band while normal devices to connect to the usual 2.4 GHz band at the same time. It's like having 2 networks in 1.
Because most cordless phones and wireless security systems also use the 2.4 GHz band, there is much more wireless interference on this band. Most of the devices you list (iPhone, iPad) would not be able to connect to the 5 GHz band, so you would not need the AirPort Extreme.
If you decide to get the Express, post back if you want a step by step on how to configure the device for travel.
Message was edited by: Bob Timmons