Yeah, I've read some negative reviews, too. It sounds like Spot 2 might be okay for communicating with home (if it's not essential that the message actually get through), but not for something like, oh shall we say, getting rescued? And then there's the subscription fee--it's sorta like inkjet printers, where the printer's super cheap and the cartridges expensive. I ended up getting a PLB instead. To the tune of about 5 times what a Spot 2 costs. There is an optional subscription service for the PLB (which lets you send a limited number of communications to select recipients) that costs almost as much as the Spot's subscription service, but the PLB also works without the subscription service, whereas the Spot doesn't. I chose to use the PLB strictly as a personal locator device in case of an emergency, but I might decide to subscribe later on. The Spot doesn't do anything without a subscription.
If your main concern is being able to send rescue messages that will reliably be received, don't waste your money on a Spot. If your main concern is communicating with home, don't spend all that money on a PLB.