I recently used the InReach when sailing across the Tasman Sea.
1. It worked flawlessly for tracking as displayed on the share.delorme site
2. It's SMS text function also worked flawlessly for both incoming and outgoing messages.
3. I have no working experience with the SOS function, but given the above, I would expect it to operate appropriately.
4. It has no voice function
5. It does not receive data beyond SMS so don't expect it to receive GRIB files
6. It did everything it was advertised to do including delivery
of it's preset messages. Take note that these will not work until the device has been synchronized post any change to the stored data so do this before departure.
If you are looking for GRIB files, you'll need a separate satellite
service like offered with the Iridium
Go and Predict Wind
Personally, the SOS function is a "secondary". I'd be seeing the EPIRB
as the primary, a satellite phone
as the secondary and the InReach SOS as a second backup.