Chris,
I spoke to the chap on the roadshow in the Oracle when I took up the service about it working in a steel boat.
He said that if a mobile phone works there, the modem will. However, I do find I need to put the supplied tiny aerial in the window with the suckers supplied.
Apparently, the service is optimised for browsing and downloading so not alot of use for games playing or peer to peer downloads. Also, you are limited to 10gig per month download, but if you can live with it, it's good.
If you are in the area and fancy taking a look give me a shout. We will be in the Thames and Kennet marina for a week and then we are back on the river in the Reading area.
Thanks
Mike