I spent a night watch, crossing the Gulf of Maine, far outside cell coverage (50-60ish miles), texting friends and kids on my DeLorme. It works great. You have to wait several seconds for your message to upload and longer for the device to interrogate for incoming messages, so it's not instantaneous, like a cell network. Still, it was great. I also sent a log entry to a group of folks, every 6 hours, on our 26 hr passage. Location was automatically included in every text. I added speed, COG, general conditions and crew report. Way better than a long float plan.
Speaking of floating, I bought the lifejacket for mine, so it would float. Not sure of the Spot buoyancy. I would much rather have a DeLorme with me in a liferaft than a vhf radio. Even an EPIRB signal is going to take many hours, before SAR decides to come look for you. With a text message, I can confirm I need help immediately. That kind of confirmation is all the Coasties need.
I used my iPhone for comm, which was bluetooth connected to the DeLorme. Therefore, I left the DeLorme tethered to the cockpit table and plugged into the cig lighter most of the time. I don't think the house bank even knows its there.
It did work from down below as well, but not as reliably. The bluetooth signal was fine, but satellite upload/download was longer and failed occasionally, from the nav station. There were times, I would tether it under the dodger, just above the nav station and text from down below. That worked very well.
You can manage battery life to a degree, with user settings for how often it uploads position data and interrogates for messages. Both can be manually triggered, if you set them to extended periods for battery life, but want to check for a reply sooner. I left it on 24/7 for an entire two week trip. Battery life was never an issue. Easily got 2-3 days before needing recharging, but never really tested the limits. If one was backpacking, perhaps this is an issue, but I can't see it aboard a sailboat, with a power system.
As someone pointed out, DeLorme does allow for monthly plans, which is what I use. They pop you for a first time set up fee of something like $25 for this, but then it's just on/off, as needed. You can choose from several plans, depending on how many texts you expect. Personally, I buy unlimited, but usually for only a couple of months per year. It also allows the office to reach me, in an emergency. In coastal Maine, even some southern New England anchorages, cell coverage can be difficult. It's not just an offshore advantage.
For $1 per request, you can get a weather forecast on the DeLorme. Not awesome weather capability, but a neat backup idea. I expect this will improve over time. What I really want is a grib file, which is bandwidth limited right now. Still, it could be several messages stitched together.
As I expected, Spot coverage seems to have improved. Here is their map. Nevertheless, it has some limits, such as a Pacific crossing. Admittedly, that not very limiting for most. DeLorme is indeed full global.
Network / Satellite
Both are pretty useful devices. Fielder's choice, depending on needs.