OP I live in the Highlands (am Scottish, so is DH). It's beautiful and spacious and the wildlife is fantastic and the opportunities for outdoor activities are great. But what people say about rural remoteness is true - poor telecoms (no mobile phone signal in a fair few places), very poor broadband, narrow, dangerous, ungritted roads that can be blocked by fallen trees in winter and clogged with tourists in the summer. Local shops (if any) with costly, limited stock.
Power-cuts; no mains gas or mains drainage (septic tanks). Cultural activities a long way away.
Communities can be divided between local people/crofters and rich incomers. There are few jobs, low wages, drugs, alcohol abuse, mental health problems. Lots of road accidents. A skewed demographic - many young people move away to find good jobs, so many villages have a high proportion of over 50s or older with multiple health needs.
No supermarket deliveries in many places. Courier deliveries slow and expensive. Very few skilled tradespeople. Schools can be a very long way away - weekly boarders/long bus journeys. As so many people have said, nothing much for teenagers to do. Their best schoolfriends may live 30 miles away; there may be few other people of their age/interests close to the place where they live.
I think you also have to ask - can you contact any rural Highland GPs? - why there are so many vacancies for medics in the Highlands. Many practices have just one full-time GP, helped by part-timers or ( more often) a series of locums. Medical professionals that I've met say that they wish they had more colleagues for support - someone to discuss cases with, or someone to share a particular area of interest/expertise. Some practices have video conferences to try to address this, but I think the work can often be often lonely, and the responsibilities as a sole GP are enormous. Out of hours arrangements vary from place to place, but where I live, the GP' does daytime Mon-Fri; nights and weekends are covered by locums or nurse practitioners, who won't necessarily be local. Home visits can involve driving in hazardous conditions. There is no quick help from paramedics - it takes the local ambulance an hour to get to many villages in its 'patch'. . The nearest hospital can be hours by road or air away. (As people have said, there is one big hospital - in Inverness - for the whole of the Highlands. ) Things like bloods can take a long time to get there to be tested, though there are recent improvements - the local paper had an article only recently about a 'blood-bike' - a high speed motorbike courier service to link GPs to central hospital labs.
NHS Highland has had a very troubled time in recent years, with accusations of bullying and some very, very unhappy doctors. ( www.tsh.scot.nhs.uk/Safe/Docs/Learning%20from%20External%20Inquiry%20Reports/Sturrock%20Report%20-%20Apr%2019.pdf ) Big attempts are being made to put all this right, but again, if you can talk to current Highland GPs about how well these are working, it would probably be very useful.
The Highlands can be fantastic, and I love living here, but it is not always easy. It depends, I suppose, on what you like. Some people positively thrive on challenges.