I have been watching and waiting for this GPS to come out for some time, and what will be the clincher is if it has great maps. If it fails in the mapping department, than I have come to the conclusion of going with Delorme's PN-20 as it suits my needs for hiking/camping.
As for additional information on the Onix400, I read that the XM weather subscription could be "seasonal" if a person does not need it all year long, and that reactivating the service would not require a restarting fee. For me, the ultimate GPS would be one made with Garmin quality, the maps of Delorme's PN-20, and the weather radar of the Onix400