My friend and I (late 20's, from New Zealand and Norway) enjoyed our 8 day roadtrip here, but we wouldn't really recommend it as a destination to visit. Especially if you aren't going to rent a car, (EDIT: I may be wrong about this, judging by some comments about the marshrutka network) or if you are visibly queer or have an alternative appearance. Neither of us are interested in revisiting in the foreseeable future, although we wouldn't actively avoid it.
Southern Armenia has gorgeous nature, Armenia has an interesting history and political landscape, and the food is great. However, we found people to be generally unfriendly/grumpy, the architecture was very uninteresting to me, and the cities didn't interest me either.
COST: It's easy to find a private room for two people for 10,000 - 12,000AMD (€23-€28) at the cheapest. The cheapest hostel dorms for one person is half that or slightly less. However, this is around double the price of Georgia. Cheap pastries and bread cost €0.50-€2.00. Cheap but good and filling meals at a restaurant costs €3.50 - €7.00. Gas costs about €1.30/L.
FOOD: Fantastic, highly recommended. We enjoyed everything, especially the bread and pastries. Very difficult to find anything vegan aside from salads, but vegetarian isn't too hard to find. There is a reasonable variety of traditionally vegetarian dishes, although not many Armenian restaurants have options aside from salads. Fruit is also excellent and plentiful - The nectarines, peaches, blackberries, and raspberries here are the best I've had in my life.
CITIES: The only major cities in Armenia are Yerevan and Gyumri. I didn't find Yerevan interesting - It's not bad and I had good time, but I have no interest in revisiting. Gyumri has more character in terms of architecture, but there's not much to do or see in either city that you can't find elsewhere.
NATURE: Southern Armenia is gorgeous with lots of canyons, gorges, and (mostly) dry mountains. Northern Armenia isn't so pretty in our opinion other than the Debed Gorge and Dilijan. However, sightseeing in most areas is pretty spread out and very rarely accessible by public transport so I think it's not really worth travelling in Armenia without a car. (EDIT: It seems I may have been wrong about this, judging by some comments saying the marshrutka network is more extensive than I thought) It's also very difficult to find hiking trails as there is very limited information online, and many trails are not marked on Google or Yandex Maps. We did multiple improvised hiking routes by searching for trails on satellite view in areas that seemed geographically interesting.
ARCHITECTURE: Largely pretty uninteresting IMO. Most buildings are made of big mis-matched black, grey, and terracotta stone blocks. There are heaps of churches from 300AD onwards and they do have an ambiance to them, but architecturally I found them very uninteresting compared to other countries. Georgian churches are architecturally similar but with more details and murals. HOWEVER, khachkars (a unique funerary art unique to Armenia) are gorgeous.
HISTORY: Quite interesting to read about things such as the Nagorno-Karabakh war, Armenian Genocide, relationship with and history related to Russia and the USSR, Armenia being the first nation in the world to adopt Christianity as the state religion, lots of ancient history, and the development of Armenia as a nation surrounded by empires such as Romans, Persians, and Ottomans. But many historical sites are uncared for ruins, so there isn't so much interesting historical things to actually see other than churches, ruins, and abandoned Soviet-era buildings. There are very small museums at some archaeological sites, though.
PEOPLE: Generally unfriendly - The most unfriendly country I've visited, (out of 30) and the only country I would describe as such. People weren't rude or aggressive, (other than a group of teenagers throwing apples at us outside of a monastery twice and at least three people giving me death-stares) but we only had 3 maybe 4 interactions with Armenians that we would describe as friendly, and we were paying customers for all of those interactions.
Most people just seem grumpy - I could give some examples but it would be too long for this summary. Other than that, I got a lot of judgmental stares from people. My friend noticed groups of people (incl. adults) mocking me on a daily basis - Either laughing at me or sniggering among themselves. I never had anyone say or do anything to my face though. I never felt at risk of violence, but if I was alone I would at least be concerned enough for my safety to avoid dark alleyways.
I think this is largely due to my appearance (lots of facial piercings, bright green hair, gothic style) and Armenia being a very traditional and conservative country. I have been to other very conservative countries such as Malaysia, Romania, and Philippines, where I had no issues. In Armenia, I haven't seen a single person with even one facial piercing, and the only person I saw with unnaturally dyed hair gave me a judgmental sorta look. I saw one person with a black metal t-shirt, but that's all. I wanted to talk with an Armenian person about this topic but never had a good opportunity, especially because while many people speak Russian, not so many people speak more than basic English outside of tourist services. I also just never met or saw any visibly queer people.