Sorry to be the bearer of bad news, but HEMS is currently in a "bubble." As an example, you look at Philadelphia (where I'm from) and you'll see 6-7 helicopters all covering the same territory, based on a 10(!) minute flight time. If you were to open that up to a more reasonable 20 to 30 minute response time, there would be over a dozen helicopters (probably 16-18) all vying for the same territory and business. This is for an area where you can spit and hit a trauma center or burn center, either adult or pediatric. That level of "service" isn't viable.
Out in the sticks, there is more of a need, but it is harder to support the service, plus you have a more "rural" attitude towards emergencies. People who live 90 minutes from the nearest town tend to accept that it's gonna take a while to get to the hospital. The problem though is that these areas can't support a flight service based on call volume. Prehospital response can't support a helicopter, and there isn't large enough interfacility need in the country. If a helicopter doesn't make money, it isn't in business (medicine is a for-profit venture, y'know.)
The problem is, most of the HEMS interfacility transports are unnecessary, and largely for the conveience of the hospital rather then a need for urgent transportation (as strangely, some of the most critical cases aren't stable enough to go by air). Insurers (and patients,) who are getting stuck with ridiculous transportation costs, have already been paying close attention to reimbursements, and while they haven't really pushed back yet, you can feel it hanging there. With ObamaCare, a lot of changes are going to occur with insurers (as they will likely get more power then they currently have over the practice of medicine) and HEMS will take a hit (it's inevitable).
That's going to mean a lot less jobs for flight nurses/medics, and lower pay as well (as people would do it for free if you let them). It's not a career field I'd want to aspire to. Ground critical care, on the other hand, may become a big deal, but that's another post, and not at all sexy.