Wifi for Boats, Bitstorm, IslandtimePC (and possibly WaveRV) all use the exact same Ubiquity hardware with an external higher gain antenna. These units work off web browsers and require no drivers - so it doesn't matter what computer platform they are used with. Wirie uses Alfa gear with an antenna and waterproofing.

The second USB plug on the Alfa is for providing power when used with computers containing USB ports that do not provide the standard 500mW of power. These are older ports and unlikely to be on any computer manufactured in the past 3 years. So most likely, you will never need to plug both in.

Wirie also makes a unit with a built-in repeater that allows wireless access and simple installation (a single 12V power line).

Your success with wifi will be completely dependent on the gear you chose and how you mount it.

If you get an Alfa straight out of the box and simply place it in the cockpit or outside a hatch, you will get better connections than your base computer, but be leaving a lot of goods on the table.

If you add a proper high gain antenna (not the "high gain" rubber ducky thing that Alfa sells), you will get back some of those goods provided you do NOT use coax cable to get distance from the antenna (any coax should be a 6" pigtail connector only).

If you buy or make a system like the Wirie, Bitstorm, IslandTimePC, etc, using the Alfa or Ubiquity gear, adding a proper high gain antenna and (semi)permanently mounting it in a spot 10' or so off the water and with clear sight, you will have given it your all.

We are in the third category and regularly connect 3-5 miles away from home routers buried deep in houses. If there is a public access point, we connect even further (5-7 miles is usual and routine if we have line of sight). Our record was 36 miles off the coast of New Jersey connected to a beach hotel that beamed wifi from its roof to its guests on the beach and roof pool/bar.

However, we now cruise where there is no wifi and have discovered cell-based mifi and how to build a good system using an external high-gain antenna, waterproofing, proper mounting, etc (sound familiar?). Here in Panama, sim cards are free and data plans are cheap and there are no contracts - and it is this way throughout the Carib. US prices for data plans are eye-popping and you are locked into a single carrier with long contracts. Anyway, with the proper gear, we now anchor in places where others have no cell connection and surf the web wirelessly without a tether to a phone.

Mark