satisfied (Well, kinda)
As a mac geek and web junky, i can say that this is probably the best team-up i could suggest. look, not to say that everything is perfect with their service, but I have experienced very little down-time (a few minutes over 18 months) and there help-desk are typical PC-usuals who either assume that you haven't exhausted their FAQ section or other material before calling them, only to be told exactly what was on the FAQ.
only problem though is that it doesn't work with the new intel machines, since rosetta doesn't translate the driver yet. Japan are working on it, and shouldn't take too long. certainly not as long as waiting for ADSL.
not sure about sentech, but aside from the hefty relative price and unstable nature, i doon't think it plays with mac.
you could use the desktop version with either usb or ethernet connection, and i find the latter to be a little faster when i have another usb device connected. but i've clocked 1mbs on both. before there were 800 too many users per tower... it even works beautifully for a small network coupled with an ethernet router, and more impressively with an airport network.
so yes. it works. and there are a few happy customers i know personally. as for coverage, look on their coverage map:
http://www.iburst.co.za/mapsystem/index.html didn't look too bad in areas, and there should be more towers going up soon - but don't quote me on that