You should search more on the forums for Alaska and XM. There were a number of posts by people who said it didn’t work out and they cancelled. Enough so that I decided not to get it, even though I intended to. However, if it helps at all, why not except the pricing.
Part of the reason for not needing it is you can download by wifi at select locations before the few crossings you need the info and the 3 day forecast is really good on those services.
Others complained about poor or not updated data, and satellite availability the further north you go.